Two computers working together can finish a search in 30 seconds. one of these computers can finish in 50 seconds. how long would it take the second computer to finish the same search if it were working alone?

Let x be the first computer. Let y be the first computer. We know that Work = 1 / Time.

If the work together, work can be done in 30 seconds. Thus, we have:
1/x + 1/y = 1/30

If x will finish in 50 seconds, we need to compute how many seconds y can finish the same work. Thus solving for y, we have the equation below:
1/50 + 1/y = 1/30
1/y = 1/30 - 1/50
1/y = 1/75

The second computer can finish the same work in 75 seconds.