At least 2 women means that the committee contains 2, 3, 4 or 5 women
P(2 women) = C(16,3) * C(12, 2) / C(28,5)
P(3 women) = C(16,2) * C(12,3) / C(28,5)
P(4 women) = C(16,1) * C(12,4) / C(28,5)
P(5 women ) = C(12,5) / C ( 28,5)
So....the total probability is
[ C(16,3)* C(12,2) + C(16,2)*C(12,3) + C(16,1) * C(12,4) + C(12,5) ] / C(28,5) =
11 / 15