My first smart contract!

Addition.sol

pragma solidity ^0.4.18;

contract Addition {
    uint sum;

   function Addition() payable public {

   }

   function () payable public {

   }


   function add(uint _one, uint _two) public {
       sum = _one + _two;
   }

   function getSum() public view returns (uint) {
       return sum;
   }
}

GuessMonth.sol

pragma solidity ^0.4.18;

contract GuessMonth {

    uint month;
    uint oneEther = 1000000000000000;
    address owner;
    
    event GuessMade(string correctOrNot); // Event
    event MonthChanged(string textToLog); // Event

    modifier onlyOwner() {
        if (msg.sender != owner) {
            revert();
        }
        _;
    }

    function GuessMonth (uint _month) payable public {
        month = _month;
        owner = msg.sender;
    }

    function sendGuess(uint _guess) payable public {
        if (month == _guess) {
            GuessMade("Correct!");
            msg.sender.transfer(2 * oneEther);
        } else {
            GuessMade("Incorrect!");
        }
    }

    function chnageMonth(uint _newMonth) onlyOwner public {
        month = _newMonth;
    }
    
    function getMonth() public view returns(uint) {
        return month;
    }
}