I am guessing it is b! because BG and BA are sides, and BAU and BGN are angles.
To solve this problem, just use multiplication.
You can somewhat think of this situation as a sort of tree. You start with 7 large branches representing the pants, then for every one of those you have 3 medium-sized branches to represent the pairs of pants. Each one of those has 5 sticks for the ties, which in turn each have 6 leaves to represent the jackets and therefore a complete outfit. The solution is found by getting the total number of leaves on the tree.
The answer is the second one
(a) The probability of drawing a blue marble at random from a given box is the number of blue marbles divided by the total number of marbles. We assume that the probability of selecting one of two boxes at random is 1/2 for each box.
... P(blue) = P(blue | box1)·P(box1) + P(blue | box2)·P(box2) = (3/8)·(1/2) + (4/6)·(1/2)
... P(blue) = 25/48 . . . . probability the ball is blue
(b) P(box1 | blue) = P(blue & box1)/P(blue) = (P(blue | box1)·P(box1)/P(blue)
... = ((3/8)·(1/2))/(25/48)
... P(box1 | blue) = 9/25 . . . . probability a blue ball is from box 1
