diff --git a/src/calculator.js b/src/calculator.js
index b46080e5..30bd0fdb 100644
--- a/src/calculator.js
+++ b/src/calculator.js
@@ -1,48 +1,30 @@
-exports._check = () => {
-  // DRY up the codebase with this function
-  // First, move the duplicate error checking code here
-  // Then, invoke this function inside each of the others
-  // HINT: you can invoke this function with exports._check()
+exports._check = (x, y) => {
+	if (typeof x !== 'number') {
+		throw new TypeError(`${x} is not a number`);
+	}
+	if (typeof y !== 'number') {
+		throw new TypeError(`${y} is not a number`);
+	}
 };
 
 exports.add = (x, y) => {
-  if (typeof x !== 'number') {
-    throw new TypeError(`${x} is not a number`);
-  }
-  if (typeof y !== 'number') {
-    throw new TypeError(`${y} is not a number`);
-  }
-  return x + y;
+	exports._check(x, y);
+	return x + y;
 };
 
 exports.subtract = (x, y) => {
-  if (typeof x !== 'number') {
-    throw new TypeError(`${x} is not a number`);
-  }
-  if (typeof y !== 'number') {
-    throw new TypeError(`${y} is not a number`);
-  }
-  return x - y;
+	exports._check(x, y);
+	return x - y;
 };
 
 exports.multiply = (x, y) => {
-  if (typeof x !== 'number') {
-    throw new TypeError(`${x} is not a number`);
-  }
-  if (typeof y !== 'number') {
-    throw new TypeError(`${y} is not a number`);
-  }
-  return x * y;
+	exports._check(x, y);
+	return x * y;
 };
 
 exports.divide = (x, y) => {
-  if (typeof x !== 'number') {
-    throw new TypeError(`${x} is not a number`);
-  }
-  if (typeof y !== 'number') {
-    throw new TypeError(`${y} is not a number`);
-  }
-  return x / y;
+	exports._check(x, y);
+	return x / y;
 };
 
 module.exports = exports;
diff --git a/src/calculator.test.js b/src/calculator.test.js
index d0f85ed6..3d6b7f74 100644
--- a/src/calculator.test.js
+++ b/src/calculator.test.js
@@ -1,7 +1,7 @@
 /* eslint-disable no-unused-expressions */
 const calculator = require('./calculator');
 
-describe.skip('_check', () => {
+describe('_check', () => {
   beforeEach(() => {
     sinon.spy(calculator, '_check');
   });