.
The probability that a typist will make at most 5 mistakes when typing a report is 0.59
and the probability that she will make 6 to 10 mistakes is 0.26.
Find the probability that the typist will make at most 10 mistakes.
~~~~~~~~~~~~~~~
The event making at most 10 mistakes is the UNION of two disjoint events:
1) making at most 5 mistakes, which has the probability of 0.59 (given),
and
2) making 6 to 10 mistakes, which has the probability of 0.26 (given).
THEREFORE, the answer to the problem's question is the sum of probabilities
P = 0.59 + 0.26 = 0.85.
Solved.
Very nice joke problem.