The probability that she chooses a black dress is 40% or 40/100
The probability that her parents approve of the black dress is 30% or 30/100
The probability that she chooses a black dress and her parents approve is the probability of choosing a black dress times the probability of her parents approving of a black dress, which is 40/100 x 30/100

So the probability that Sue chooses a black dress that her parents approve is
12%