George has 9 more dollars than frank, who has 3 more than richard. what is the least amount of money that must be exchanged so that they each have the same amount of money?
i know the answer is $7 but is there a quicker way to do it instead of guess and check?

R+r+3+r+12

3r+15, let r=1

3+15=18, so we need each person to have 6

we know that g=12+1=13, f=3+1=4, r=1

So g must give away 7. f must take 2, and r must get 5

So 7+2+5=14 got exchanged in total.

But I can see that only $7 dollars was taken to be distributed to the other two as well.