Pump A empties water from a pool in 6 hrs. When Pump B is used with Pump A, the pool is empty in 1.5 hrs. How long does it take Pump B to empty the pool alone?

Question

I do not really know where to start with this problem.

Answer 1

1.5 / 6 + 1.5 / B = 1

1.5B + 9 = 6B

9 = 4.5B

2 = B