So the question of what proportion of adults have a body temperature above 98.6 degrees translates into
"What is the probability that X > 98.6, where X has a Normal distribution with mean 98.6 and standard deviation 0.8? "
To answer this by looking up probabilities in a table of the cumulative Normal(0,1) distribution, you would consider , which has a Normal(0,1) distribution.
(Actually, since 98.6 is the mean, you don't even need a table or knowledge of the standard deviation for this part of the question , but you will need it for the next.)
Can you take it from there?