If you attempt 1 question, there are 2 ways to answer that question but there are 6 questions that could have been chosen to answer. So for line 2, it should be 1\*2!\*(6C1). This is the error in the way you constructed your answer.

As another poster has pointed out, a simpler way to get to the answer is to consider that for every question, there are three options - don't answer, answer T or answer F