Using the combination formula, it is found that she can select the shirts in 775,200 ways.
The order in which the shirt are chosen is not important, hence, the <em>combination formula</em> is used to solve this question.
Combination formula:
is the number of different combinations of x objects from a set of n elements, given by:
In this problem:
- 3 shirts from a set of 17.
- Then, 3 shirts from a set of 20.
- They are independent, hence, to find the total, we multiply both combinations.
She can select the shirts in 775,200 ways.
To learn more about the combination formula, you can check brainly.com/question/25821700