6 shirts 4 different pairs of pants, how many different combinations could she wear?

The shirts can be called A, B, C, D, E, F.

the pants can be called 1, 2, 3, 4.

if you combine these together you get

A1, A2, A3, A4, B1, B2, B3, B4, C1, C2, C3, C4, D1, D2, D3, D4, E1, E2, E3, E4, F1, F2, F3, F4 OR 24

You get 24 outfits.