Mary has 40% fewer marbles than Jolie. If they combine all their marbles in a single bag, what percent of the marbles in the bag are Jolie's?

The easiest way to do this would be to imagine that Jolie has 100 marbles. If Mary has 40% fewer, that means she has 60 marbles. Then if they combine all their marbles into a single bag, they will have 160 marbles, of which 100 are Jolie's. So the % that is Jolie's is 100/160 = 0.625 = 62.5%.