implemented simple operations

src/operations/add.js

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+const add = (addend1, addend2) => {
+  return addend1 + addend2;
+};
+
+module.exports = add;

src/operations/divide.js

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+const divide = (dividend, divisor) => {
+  if (divisor === 0) {
+    throw new Error('Cannot divide by 0');
+  }
+  return dividend / divisor;
+};
+
+module.exports = divide;

src/operations/index.js

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+const add = require('./add');
+const divide = require('./divide');
+const multiply = require('./multiply');
+const subtract = require('./subtract');
+
+module.exports = {
+  add,
+  divide,
+  multiply,
+  subtract,
+};

src/operations/multiply.js

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+const multiply = (multiplicand, multiplier) => {
+  return multiplicand * multiplier;
+};
+
+module.exports = multiply;

src/operations/subtract.js

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+const subtract = (minuend, subtrahend) => {
+  return minuend - subtrahend;
+};
+
+module.exports = subtract;