diff --git a/lib/formula_evaluator.dart b/lib/formula_evaluator.dart
index f985479..91f7914 100644
--- a/lib/formula_evaluator.dart
+++ b/lib/formula_evaluator.dart
@@ -117,9 +117,7 @@ class FormulaEvaluator {
     } catch (e, stack) {
       // SPECIAL CASE: If the error message starts with signalMagicString, treat it as a signal message and return it instead of throwing an exception
       // SEE signal() function in the generated d4rt code above for how this is used
-      print("#######################");
       if (e.toString().contains(signalMagicString)) {
-        print("***********************");
         final signalMessage = e.toString().split(signalMagicString).last.trim();
         return signalMessage;
       }
@@ -295,6 +293,52 @@ class FormulaEvaluator {
   }
 }
 
+Number formulaSolver(Formula formula,
+    String variableToSolve,
+    Map<String, dynamic> fixedInputValues, {
+      Number hint = 0,
+      Number step = 10,
+      Number maxDelta = 0.01,
+      int maxTries = 100,
+    }) {
+  
+  if( variableToSolve == formula.output.name ){
+    return FormulaEvaluator().evaluate(formula, fixedInputValues);
+  }
+  
+  if (!formula.inputVarNames().contains(variableToSolve) ){
+    throw ArgumentError(
+      'Variable "$variableToSolve" is not an input or output variable of the formula "${formula
+          .name}".',
+    );
+  }
+
+
+  final modifiedInputValues = Map<String, dynamic>.from(fixedInputValues);
+  var evaluator = FormulaEvaluator();
+  Number f(Number x) {
+    modifiedInputValues[variableToSolve] = x;
+    final result = evaluator.evaluate(formula, modifiedInputValues);
+    if (result is Number) {
+      return result;
+    } else {
+      throw FormulaEvaluationException(
+        'Expected formula evaluation to return a number, but got: $result ${result.runtimeType}',
+      );
+    }
+  }
+
+  var fixedFormulaOutput = fixedInputValues[formula.output.name];
+
+  return functionSolver(
+    (Number x) => f(x) - fixedFormulaOutput,
+    hint: hint,
+    step: step,
+    maxDelta: maxDelta,
+    maxTries: maxTries,
+  );
+}
+
 class NoSolutionException implements Exception {
   final String message;
 
diff --git a/test/formula_solver_test.dart b/test/formula_solver_test.dart
index 2714a5f..b0407ae 100644
--- a/test/formula_solver_test.dart
+++ b/test/formula_solver_test.dart
@@ -5,53 +5,75 @@ import 'dart:math' as Math;
 
 
 void main() {
-  test("Solve x^2", () {
-    Number f(Number x) => x*x;
-    var root = functionSolver(f, hint: 10, step: 1);
-    expect(root, closeTo(0, 0.1));
+
+  group("Formulas", (){
+
+    test("Solve x^2 formula", () {
+      final formula = Formula(
+        name: 'Test x^2',
+        input: [
+          VariableSpec(name: 'x', unit: 'scalar'),
+        ],
+        output: VariableSpec(name: 'y', unit: 'scalar'),
+        d4rtCode: 'y = x*x;',
+      );
+
+      var solution = formulaSolver(formula, "x", {"y": 25}, maxDelta: 1e-10);
+      expect( solution, closeTo(5, 1e-10));
+    });
+
   });
 
+  group('Native functions', () {
+    test("Solve x^2", () {
+      Number f(Number x) => x * x;
+      var root = functionSolver(f, hint: 10, step: 1);
+      expect(root, closeTo(0, 0.1));
+    });
 
-  test("Solve (x-1000)^2", () {
-    Number f(Number x) => (x-1000)*(x-1000);
-    var root = functionSolver(f, hint: 10, step: 1, maxTries: 1000);
-    expect(root, closeTo(1000, 0.1));
-  });
 
-  test("Solve x^2 + 1", () {
-    Number f(Number x) => x*x+1;
+    test("Solve (x-1000)^2", () {
+      Number f(Number x) => (x - 1000) * (x - 1000);
+      var root = functionSolver(f, hint: 10, step: 1, maxTries: 1000);
+      expect(root, closeTo(1000, 0.1));
+    });
 
-    expect(()=> functionSolver(f, hint: 10, step: 1), throwsA(isA<NoSolutionException>()));
-  });
+    test("Solve x^2 + 1", () {
+      Number f(Number x) => x * x + 1;
 
-  test("Solve (x-2)(x-10", () {
-    Number f(Number x) => (x-2)*(x-10);
+      expect(() => functionSolver(f, hint: 10, step: 1),
+          throwsA(isA<NoSolutionException>()));
+    });
 
-    expect( functionSolver(f, hint: 10, step: 1), closeTo(10, 0.1));
-  });
+    test("Solve (x-2)(x-10", () {
+      Number f(Number x) => (x - 2) * (x - 10);
 
-  test('Solve sqrt(x) = 2  => x = 4', () {
-    Number f(Number x) => Math.sqrt(x) - 2;
-    var root = functionSolver(f, hint: 5, step: 1);
-    expect(root, closeTo(4, 0.1));
-  });
+      expect(functionSolver(f, hint: 10, step: 1), closeTo(10, 0.1));
+    });
 
-  test('Solve sin(x) = 0 near pi (hint 3)', () {
-    Number f(Number x) => Math.sin(x);
-    var root = functionSolver(f, hint: 3, step: 1);
-    expect(root, closeTo(Math.pi, 0.01));
-  });
+    test('Solve sqrt(x) = 2  => x = 4', () {
+      Number f(Number x) => Math.sqrt(x) - 2;
+      var root = functionSolver(f, hint: 5, step: 1);
+      expect(root, closeTo(4, 0.1));
+    });
 
-  test('Solve tan(x) = 1 => x = pi/4', () {
-    Number f(Number x) => Math.tan(x) - 1;
-    var root = functionSolver(f, hint: 0, step: 1);
-    expect(root, closeTo(Math.pi / 4, 0.01));
-  });
+    test('Solve sin(x) = 0 near pi (hint 3)', () {
+      Number f(Number x) => Math.sin(x);
+      var root = functionSolver(f, hint: 3, step: 1);
+      expect(root, closeTo(Math.pi, 0.01));
+    });
 
-  test('Solve exp(x) = 2 => x = ln(2)', () {
-    Number f(Number x) => Math.exp(x) - 2;
-    var root = functionSolver(f, hint: 1, step: 1);
-    expect(root, closeTo(Math.log(2), 0.01));
+    test('Solve tan(x) = 1 => x = pi/4', () {
+      Number f(Number x) => Math.tan(x) - 1;
+      var root = functionSolver(f, hint: 0, step: 1);
+      expect(root, closeTo(Math.pi / 4, 0.01));
+    });
+
+    test('Solve exp(x) = 2 => x = ln(2)', () {
+      Number f(Number x) => Math.exp(x) - 2;
+      var root = functionSolver(f, hint: 1, step: 1);
+      expect(root, closeTo(Math.log(2), 0.01));
+    });
   });
 
 }