Together, the two pipes fill the pool in 15 minutes. The first pipe can fill the pool in 15 minutes

Together, the two pipes fill the pool in 15 minutes. The first pipe can fill the pool in 15 minutes, how many minutes the second pipe can fill the pool?

First, we need to calculate the part of the work performed with the joint efforts of the pipes.
1) 1/20 + 1 / x = 1/15 (part) – work done with the joint efforts of the pipes.
Now, knowing the joint performance, it is possible to figure out the work that was done by the second pipe.
2) 1/15 – 1/20 = 1/60 (part) – the second pipe did the job.
It remains only to find out the answer to the problem question. How long does it take for the second pipe to fill the pool.
3) 1: 1/60 = 1 * 60 = 60 (minutes) – the second pipe does its job.
Answer: in an hour, the pool will be filled with a second pipe.