Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.4.24+commit.e67f0147.js&optimize=false&gist=

ballot.sol

pragma solidity ^0.4.0;

contract Dog {
    
    string output = "I'm a dog.";
    uint posNumber = 2;
    bool isDog = true;
    int number = 1;
    
    //"view" promises not to modify the contract state, it's a getter - won't consume any ether
    function bark() view returns (string) {
        return output;
    }
    
    function setOutput(string _output) {
        output = _output;
    }
    
}

Person.sol

pragma solidity ^0.4.0;

contract PersonContract {
    
    struct Person {
        string name;
        uint age;
    }
    
    Person[] people; 
    
    function addPerson(string _name, uint _age) {
        people.push(Person(_name, _age));
    }
    
    function getAverageAge(uint _id) view returns (uint) {
        uint totalAge = 0;
        for (uint i=0;i<people.length;i++) {
            totalAge += people[i].age;
        }
        
        return totalAge / people.length;
    }
    
}