Class 6S and Class 6T have a total of 20 students. ¹₃ of the students in Class 6S and ⁵₇ of the students in Class 6T are boys. The number of girls in Class 6S is equal to the number of girls in Class 6T. Find the total number of girls in the 2 classes.
Fraction of Class 6S that are girls
= 1 - ¹₃ 
= ²₃

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

The numerators are the same.  

²₃ Class 6S = ²₇ Class 6T 

Number of students in Class 6S = 3 u
Number of students in Class 6T = 7 u

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

10 u = 20

1 u = 20 ÷ 10 = 2

Number of girls in Class 6S =2 u
Number of girls in Class 6T =2 u

Total number of girls
= 2 u + 2 u
= 4 u
= 4 x 2
= 8

Answer(s): 8