Answer :

12 possible outcomes.

Sweater A
Sweater B
Sweater C

Skirt 1
Skirt 2
Skirt 3
Skirt 4

Possible ways:

A1, A2, A3, A4
B1, B2, B3, B4
C1, C2, C3, C4

AL2006

She can choose any one of 3 sweaters. For each choice of sweater . . .

She can choose any one of 4 skirts.

The total number of different ways to choose an outfit = (3 x 4) = 12 .