Consider the question. Trevor buys three bouquets of carnations. The first included 9 carnations, and the second included 14 carnations. If the average number of carnations in the bouquets is 12, how many carnations were in the third bouquet?
 If the answer is '13'; explain the reasoning:
There are 3 bouquets. The total is the average times the number of bouquets, or 12 * 3 = 36. There are 9 + 14 = 23 accounted for. The third included 36 - 23 = 13 carnations.