Lets see
a) 4 people are chosen from 14
That is just 14 choose 4 = 14C4 = 1001 (it is not really choose, C stands from combinations)
You say you get that?
b) 2 of the candiates do not want to go together.
ok Let's say those 2 are BOTH chosen
Then there will be 2 chosen out of the remaining 12 which is 12C2 = 66
BUT those are the combinations that are NOT allowed so the number of possible combinations will be
14C4 - 12C2 = 1001 - 66 = 935
Does that help?