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%.
