Class 4A and Class 4B have a total of 36 students. ¹₄ of the students in Class 4A and ⁵₈ of the students in Class 4B are girls. The number of boys in Class 4A is equal to the number of boys in Class 4B. Find the total number of boys in the 2 classes.
Fraction of Class 4A that are boys
= 1 - ¹₄ 
= ³₄

Fraction of Class 4B that are boys
= 1 - ⁵₈ 
= ³₈ 
 
The number of boys in Class 4A is equal to the number of boys in Class 4B.

The numerators are the same.  

³₄ Class 4A = ³₈ Class 4B 

Number of students in Class 4A = 4 u
Number of students in Class 4B = 8 u

Total number of students 
= 4 u + 8 u
= 12 u

12 u = 36

1 u = 36 ÷ 12 = 3

Number of boys in Class 4A =3 u
Number of boys in Class 4B =3 u

Total number of boys
= 3 u + 3 u
= 6 u
= 6 x 3
= 18

Answer(s): 18