This riddle was posted to Facebook with the claim that only one in a thousand will figure it out. What do you think the answer is?

1 + 4 = 5
2 + 5 = 12
3 + 6 = 21
8 + 11 = ?The answer that jumped into my mind is to add the first number to the product of the two numbers to get the answer. That is: a + b means a + ab
This works for the known equations.
1 + 4 means 1 + 1(4) = 5
2 + 5 means 2 + 2(5) = 12
3 + 6 means 3 + 3(6) = 21

Applying the pattern to the last equation gives the answer of 96.
8 + 11 means 8 + 8(11) = 96