How many bit strings of length six either begin with two 0s or end with three 0s?
This tells me that there are only two option available to begin with, 0 or 1.
For it to start with 2 0's, it would be 2^4=16
For it to end with 3 0's, it would be 2^3=8
Subtract 2^1 for the two instances that would have two 0's in the front and three 0's in the back.
Is that correct?