15 take math only 
8 take bio only 
8 take tech only 
4 take bio and math 
7 take math and tech 
6 take bio and tech 
2 take all 



15 take math only, so put 15 in region a 
8 take bio only, so put 8 in region c 
8 take tech only, so put 8 in region g
2 take all, so put 2 in region e



4 take bio and math, so put 4 in region b 
7 take math and tech, so put 7 in region d 
6 take bio and tech, so put 6 in region f

 

Let's add all those:

15+4+8+7+2+6+8 = 50

what is the percentage of the students take math OR tech

They all take math or tech except for the 8 who take
bio only.  So 50-8 or 42 out of 50 take math or tech.





50x = 4200
  x = 84

Answer 84%

Edwin