First, you have to find how much each ticket costs. Bob has 20 dollars, and he spends 2/5 of it on the movie ticket. To find this, you can simply do 20*(2/5). You can also see that 1/5 of 20 dollars is 4 because 20/5=4. He used 2/5 which is double of 1/5 which means the ticket is 2*4=8. Using both methods, your answer will be, the movie ticket is 8 dollars.
Since the problem says that the tickets were the same amount of money, you can make the equation: 8=y*(4/15). The 8 stands for the price of the movie ticket, the y stands for how much money Bill has, and the 4/15 stands for the fraction of Bill's money spent on the movie ticket. As shown above, y*(4/15) will tell you how much 4/15 of y is.
Solving for y, you get 30. In conclusion, Bill has 30 dollars.
This is my FIRST every response to a question so hopefully this helps :)
(I do all my calculations on paper so you should probably solve the equations yourself to make sure I didn't make any silly mistakes.)