Ritz can eat 8 apples in 15 minutes. how long does it take to eat 16 apples at same rate?

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?

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

Need plz been trying to do it for a long time and still haven’t succeeded