In a group of 20 students, 7 study both Art and Biology. 5 study Biology but not Art.
8 study neither subject.
Given that a randomly selected student studies Art, what is the probability the student studies Art and Biology?​

Can somebody me out with this question

Aswimming pool has an input pump for filling the pool and an output pump for emptying the pool. the input pump can fill the pool in 3 hours, and the output pump can drain the pool in 5 hours. as you go to bed, the pool is full, but a neighbor’s kid turns on the output pump. at midnight, you awake to find the pool half empty. immediately, you turn on the input pump, but you are sleepy and forget to turn off the output pump. at what time will the pool become full?

The perimeter of a movie screen is 54 meters. the screen is 18 meters wide. how tall is it?