we can use Bernoulli trials here.

recall that by the method of Bernoulli Trials we have that, the probability of successes in trials is given by:

where is the probability of success, and is the probability of failure.

Let recovery be a success here. thus p = 0.8, and q = 0.2 and n = 20

this isA. What is the probability that exactly 14 recover?

this isB. What is the probability that at least 10 recover?

this isC. What is the probability that at least 14 but not more than 18 recover?

this isD. What is the probability that at most 16 recover?

this is a lot of computation, but you can reuse values, so it's not that bad