In order to solve this problem,
Add the Number in the Ratio together
3+2=5
In the problem it tells you that the combined money is 180
Let x be the "1" in the ratio
Divide to find x
5x=180
5x÷5= 180÷5
x=36
So now you know how much "1" is
John= 3×36= 108
Peter= 2×36= 72
108-72
The answer is 36