Whats the square root of 20

Liam's parents are driving three times as fast as liam is biking, but they left later than he did. if his parents caught up with him two hours after he left, how much later than liam did they leave?

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?

With this question! what is process of elimination? ? p.s. my brothers acc got banned so add his new one @ yamauchiyamyam17