I think the answer is -84
50 out of 100 is half of the class; half of the circle will represent students going to college. 25 is a quarter of the class; a quarter of the circle will represent students not going to college. 25 is a quarter of the class; a quarter of the circle will represent students undecided about going to college.
The circle graph should look something like this:
If you have a question to ask, then what is it ?
I notice that IF AB and DE are parallel, then the two triangles tip to tip at C are similar. That may help you.
28 = 3x+4x
x = 4
3x = 12
4x = 16
12:16 = 3:4
Add the 28 and 42
then divide by 2
there should be 35 kids in group