Question 1165680
Probability misses once in first 9 times is 9*0.8^8*0.2, the binomial formula. That is 0.3020.
The miss on the 10th has probability 0.2. That is multiplied by the first value to get 0.0604, the answer, assuming independence, which allows us to multiply these.

making all 20 is probability 0.8^20, or 0.0115.
making 19 is 20*0.8^19*0.2=0.0576
that sum is 0.0691

The last is Poisson, since no fixed trials, proportional to time and theoretically could be infinite. From the calculator, 7 or fewer has probability 0.7440, so the answer is the complement of 0.2560. It is more difficult doing it by hand from 8 on because need to do many more calculations until the value is insignificant, which is around P(15).

0.2560