A committee either contains B or it doesn't. If it does, then you're not allowed to have A. If it doesn't, then you can any of the remaining nine:

(Number of committees with B and not A) + (number of committees without B) = .

Similar to the other question. You need another 2 men from the remaining 5 and another 2 women from the remaining 5. So the total number is . Now divide this number by 700 to get the required proportion.