Solution: We are given that in Jacksonville Florida, on average, 8.7 days have afternoon thunderstorms.
We know that there are 31 days in the month of July.
Therefore, the probability of afternoon thunderstorms on a randomly selected day in July month is:
P(thunderstorm) =

We have to find the probability that a randomly selected day in July will not have a thunderstorm.
P(no thunderstorm) = 1 - P(thunderstorm)


Therefore, the probability that a randomly selected day in July will not have a thunderstorm is 0.72