Okay, here we have this:
Considering the provided information we obtain that:
-The interval duration between 8 minutes and 13 minutes is 5 minutes. And the interval duration between 9 and 10 minutes is 1 minute. So, we have that the probability in this case is the ratio of the duration intervals: 1/5=0.20=20%.
Finally we obtain that the probability that washing dishes tonight will take him between 9 and 10 minutes is 20%.
