Answer:
20
Explanation:
Represent the box with x, to make it easier.
3/4 of x is 15.
Whenever we see "of", we have to think multiplication!
3/4 * x = 15
Multiply both sides by 4/3 to cancel out the 3/4 on the left side and solve for x.
x = 15 * 4/3
15 * 4/3 = 60/3 = 20
x = 20