Let's say Mary has 60 marbles and Jolie has 100 marbles (since it would work in this context). If we add them together, there are 160 marbles in total.
Because we're looking for Jolie's percentage, we need to find the value of x for:
100/160 = x/100
which we know is 62.5.
Therefore 62.5% of the marbles in the bag are Joli's.
Hope this helped!
Caffeine :)