We can quickly solve this problem by assigning hypothetical values. Suppose we let Jolie's marbles equal to 100. This would mean that Mary will have 60 since 40% of 100 is 40.
The percentage of all marbles that are Jolie's could be solved by dividing Jolie's hypothetical number of values with the total hypothetical sum of Jolie and Mary's marbles.
ANSWER: 62.5% of the marbles in the bag are Jolie's.