What is the range of the four numbers 12, 4, 9 and 15?

Explanation

The largest of the four numbers is 15 and the smallest is 4, so the range is 15 - 4 = 11. Answering 3 subtracts the entry the list opens with from the entry it closes with, 15 - 12, which only ever works by accident when a list happens to begin and end at its extremes.