Alejandria has four shirts and three pairs of pants. she says that she has seven possible combinations.

False, there are 12 possible combinations.

Step-by-step explanation:

Each pair of pants matches to each shirt.  

She has 3 pairs of pants (1, 2, & 3) and 4 shirts (A, B, C, & D).

Here are all of the combinations:

           1A       1B       1C         1D

          2A      2B       2C        2D

          3A      3B       3C        3D

There are 3 pants × 4 shirts = 12 different combinations