Class 6J and Class 6K have a total of 70 students. ¹₃ of the students in Class 6J and ⁵₇ of the students in Class 6K are boys. The number of girls in Class 6J is equal to the number of girls in Class 6K. Find the total number of girls in the 2 classes.
Fraction of Class 6J that are girls
= 1 - ¹₃ 
= ²₃

Fraction of Class 6K that are girls
= 1 - ⁵₇ 
= ²₇ 
 
The number of girls in Class 6J is equal to the number of girls in Class 6K.

The numerators are the same.  

²₃ Class 6J = ²₇ Class 6K 

Number of students in Class 6J = 3 u
Number of students in Class 6K = 7 u

Total number of students 
= 3 u + 7 u
= 10 u

10 u = 70

1 u = 70 ÷ 10 = 7

Number of girls in Class 6J =2 u
Number of girls in Class 6K =2 u

Total number of girls
= 2 u + 2 u
= 4 u
= 4 x 7
= 28

Answer(s): 28