# of people that have waited more than 5 minutes - # of people that have waited more than 10 minutes = # of people that have waited between 5 and 10 minutes.

(a) Label the next two equations for easy reference.
.12*total = # of people that have waited more than 5 minutes
.04*total = # of people that have waited more than 10 minutes.

(1) total = # of people that have waited for less than 5 minutes + # of people that have waited for more than 5 minutes.

total = 88 + .12total
.88 total = 88
total = 100

Since we now know the total, we can get numbers for both parts of (a), and answer the question. This statement is sufficient.

(2).04 total = 4
total = 100.

Again, you can get numbers for both parts of (a) and answer the question. This statement is sufficient.

The answer is D. Note that the answer to the question is 8, but you don't need to work it out.