Question

Jar B has 20% more marbles than jar A. What percent of the marbles in jar B have to be moved to jar A, in order for the number of marbles in both jars to be equal?

Answer 1

Lets see if the next procedure can explain what you need:
Try have A contain, for example, 100
B has 20% more: 20% is 20/100 or 0.20
20% of 100 = 0.02*100= 20
 so B has 100+20 = 120 to make the number equal you want to move 10 from B to A so both have 110
I Hope this can help you