First we should look at the prime numbers (numbers that can only be divded by itself and one)
1,2,3,5,7,11,13,17
Now it can't be 17 because 18-17=1, and you need one more number
It can be 13, because 18-13=5, and 5-3=2, meaning the numbers can be 2, 3, and 13
It can be 11, because 18-11=7, and 7-5=2, meaning the numbers can be 2,5, and 11
