A: We want to select one person who works out three days a week. Our probability is simply 12/80 ~~ 15%
B: At least 4 days a week means 4 days, 5 days, or 6 days. Hence, we have: (9 + 20 + 8)/80 = 46%
C: At least once a week. Let's find out how many DO NOT work out and subtract that from our sample space. This means they must work out at least once a week.
