Each of the numbers in the Pyramid can be found by adding the two numbers in the layer below it. Looking at the second layer, 7 = 3 + 4, 9 = 4 + 5, and 8 = 5 + 3, and in the third layer, 16 = 7 + 9 and 17 = 9 + 8. The top brick should then be the sum of the two below it, or 16 + 17 = 33.
