text: webDevApp.service('Maths', function (httpService) {
      var url = 'http://api.mathjs.org/v4/';
  
      var add = function add(numberOne, numberTwo) {
          return httpService.post(url, {
              "expr": numberOne + "+" + numberTwo,
              "precision": 14
          });
      }
  
      var subtract = function subtract(numberOne, numberTwo) {
          return httpService.post(url, {
              "expr": numberOne + "-" + numberTwo,
              "precision": 14
          });
      }
  
      var divide = function divide(numberOne, numberTwo) {
          return httpService.post(url, {
              "expr": numberOne + "/" + numberTwo,
              "precision": 14
          });
      }
  
      var multiply = function multiply(numberOne, numberTwo) {
          return httpService.post(url, {
              "expr": numberOne + "*" + numberTwo,
              "precision": 14
          });
      }
  
      return ({
          add: add,
          subtract: subtract,
          divide: divide,
          multiply: multiply
      });
  });