To find for the last sum of 16, 36, and 72, we need to decompose all prime factors such as shown below: 16=16,8,4,2,1 36=36,18,9,3,1 72=72, 36,18,9,3,1 x=64,32,16,8,4,2,1 The value of x is 128. Therefore, the answer to the last sum is 16, 36, 72, 128.