Question 1152816
This is 0.995 probability that an adult will not test positive.
For combining 24 people, assuming independence, the probability of not testing positive is now 0.995^24=0.8867

so the answer to the first is the complement or 0.1133
That would not be considered unlikely, although the word's definition would need to be clarified.  With a rare disease (1/2000) to have a 1/10 probability of being positive represents a considerable degrading of the test.