In a class of 100, every boy had 2 girlfriends, but no girl had more than 1 boyfriend. if exactly 13 girls had no boyfriend, then how many students in the class were girls?
the answer is 71 but i dont know how to get 71?

71 girls

Step-by-step explanation:

The class has 100 students.

It consists of 13 girls with no boyfriends, and the rest are "triplets" (B+2G groups)

If we subtract the 13 girls, the triplets must add up to 87 students.

The number of triplets is 87/3 = 29.

29(B + 2G) = 29B + 58G

The triplets consist of 29 boys and 58 girls with boyfriends.

No. of girls = girls with boyfriends + girls with no boyfriend

                   =                58              +                  13

                   = 71

There are 71 girls in the class.