There are 10 shirts that are not yellow or white.
Step-by-step explanation:
In order to find the number that are not white or yellow, first find the number that are each of those colors. To do that, multiply the total number of shirts by their fractions.
White
24 * 1/4 = 6 shirts
Yellow
24 * 1/3 = 8 shirts
Now subtract both of those from the total number of shirts.
24 - 6 - 8 = 10 shirts