Class 4Q and Class 4R have a total of 84 students. ¹₄ of the students in Class 4Q and ⁵₈ of the students in Class 4R are girls. The number of boys in Class 4Q is equal to the number of boys in Class 4R. Find the total number of boys in the 2 classes.
Fraction of Class 4Q that are boys
= 1 - ¹₄ 
= ³₄

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

The numerators are the same.  

³₄ Class 4Q = ³₈ Class 4R 

Number of students in Class 4Q = 4 u
Number of students in Class 4R = 8 u

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

12 u = 84

1 u = 84 ÷ 12 = 7

Number of boys in Class 4Q =3 u
Number of boys in Class 4R =3 u

Total number of boys
= 3 u + 3 u
= 6 u
= 6 x 7
= 42

Answer(s): 42