Answer:
You have to use the binomial distribution formula:
[tex]\frac{n!}{k!(n-k)!}p^{k}(1-p)^{(n-k)}[/tex]
where
n is the sample size: 15 flights
k is the nuber of successes: 3 flights
p is the probability of success: 0.80
[tex]\frac{15!}{3!12!}p^{3}(0.20)^{(12)}=9.5420416E-7[/tex]