Jerome takes a math course and a science course for summer school. For every 5 hours Jerome spends studying math, he studies science for 4 hours. If Jerome spent a total of 72 hours studying last week, then how long did he study math?
A. 80 hours
B. 13 hours
C. 40 hours
D. 39 hours
Let x be the number of hours Jerome studied math.
He studied science for 4x/5 hours.
The total number of hours studying is x + 4x/5 = 72.
Combining like terms, we get 5x/5 + 4x/5 = 72
Multiplying through the fractions, we get 9x/5 = 72
Dividing both sides by 9/5, we get x = 40. Answer: \boxed{40}.