Answer:
 0.98
Step-by-step explanation:
The probability one or the other will solve the problem is ...
 p(A or B) = p(A) + p(B) - p(A&B)
For independent events, ...
 p(A&B) = p(A)p(B)
so, the probability of interest is ...
 p(A or B) = 0.9 + 0.8 - 0.9·0.8 = 0.98
The probability is 0.98 that at least one of the employees will solve the problem.