Answer:
Option D is correct.
Explanation:
A team t-shirt costs $3 per adult and $2 per child.
Let the number of children be = c
Let the number of adults be = a
A team t-shirt costs $3 per adult that is 3a and $2 per child that is 2c, also given is that the total money collected is $275, so equation becomes:

On a certain day, the total number of adults (a) and children (c) who bought shirts was 100, equation becomes:

Now to know the number of children and adult, we can check by plugging in the values from options provided.
25 children and 75 adults = 25(2)+75(3)=50+225 =275
Rest options do not fulfill the requirements, so Option D is correct.