If a and b are two integers, then 3(a-b)^2 means​

Well there are many numbers, starting from 11 though 19.
11 times 2 = 22    12 times 2 = 24   13 times 2 = 26    14 times 2 = 28    15 times 2 = 30      16 times 2 = 32     17 times 2 = 34    18 times 2 = 36     19 times 2 = 38
so basically from any number from 11 through 19.
Hope i helped! :D