If the average of 12 numbers is 14 and the average of 4 of those numbers is 18, what is the average of the other eight numbers?

(8 + X + Y) / 3 = 12

multiply both sides of the equation by 3 to get 8 + X + Y = 36

subtract 8 from both sides of the equation to get X + Y = 28

So, the sum of the 2 missing numbers is 28