The key is to look for a pattern: 11, 16, 20, 25....
Notice how as we go, we are basically just adding 9's to 11, and adding 9's to 16.
So any number in the sequence will either be equal to 11 + 9x, or 16 + 9x.
We can start by dividing 9 into each answer choice and checking the remainders, then seeing if we can get either an 11 or a 16 by adding one more 9 to the remainder.
216/9 = 24, no remainder (so no possibility for a 11 or 16)
246/9 = 27, remainder 3. Even if we add 9 to that, we get 12 (so no poss. 11 or 16)
289/9 = 32, remainder 1. Adding a 9 only gives us 10.
299/9 = 33, remainder 2. Adding 9 to that gives us 11!! We have found a possible number.
