Use a binomial expansion to simplify:
(nc0)-(nc1)+(nc2)-(nc3)+...+(-1)^n (ncn)
I did this question and came up with an answer which is (1-0)^n
You have told us before in another posting that you do not understand the notation in connection with these problems.
Frankly, I cannot imagine a more irresponsible example of poor teaching.
You ought to complain to you educational authority.