The square roots of 25 are +5 and -5 .
We are dealing here with a uniform distribution ranging from 0 to 30 minutes. We need to calculate the probability that the unreliable bus will arrive before the reliable one. This probability is the area under the uniform distribution "curve" from 0 to 10 minutes. This constitutes 1/3 of the entire unform distr. curve. So the probability that the unreliable bus will arrive before the reliable one is 1/3, or 0.33. The probability that it will arrive AFTER the reliable bus is 2/3, or 0.67.
(36-4)=32
32\16=2
2-7^2=-47