Class 3K and Class 3L have a total of 36 students. ¹₇ of the students in Class 3K and ⁵₁₁ of the students in Class 3L are girls. The number of boys in Class 3K is equal to the number of boys in Class 3L. Find the total number of boys in the 2 classes.
Fraction of Class 3K that are boys
= 1 - ¹₇ 
= ⁶₇

Fraction of Class 3L that are boys
= 1 - ⁵₁₁ 
= ⁶₁₁ 
 
The number of boys in Class 3K is equal to the number of boys in Class 3L.

The numerators are the same.  

⁶₇ Class 3K = ⁶₁₁ Class 3L 

Number of students in Class 3K = 7 u
Number of students in Class 3L = 11 u

Total number of students 
= 7 u + 11 u
= 18 u

18 u = 36

1 u = 36 ÷ 18 = 2

Number of boys in Class 3K =6 u
Number of boys in Class 3L =6 u

Total number of boys
= 6 u + 6 u
= 12 u
= 12 x 2
= 24

Answer(s): 24