Class 2D and Class 2E have a total of 54 students. ¹₇ of the students in Class 2D and ⁵₁₁ of the students in Class 2E are girls. The number of boys in Class 2D is equal to the number of boys in Class 2E. Find the total number of boys in the 2 classes.
Fraction of Class 2D that are boys
= 1 - ¹₇ 
= ⁶₇

Fraction of Class 2E that are boys
= 1 - ⁵₁₁ 
= ⁶₁₁ 
 
The number of boys in Class 2D is equal to the number of boys in Class 2E.

The numerators are the same.  

⁶₇ Class 2D = ⁶₁₁ Class 2E 

Number of students in Class 2D = 7 u
Number of students in Class 2E = 11 u

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

18 u = 54

1 u = 54 ÷ 18 = 3

Number of boys in Class 2D =6 u
Number of boys in Class 2E =6 u

Total number of boys
= 6 u + 6 u
= 12 u
= 12 x 3
= 36

Answer(s): 36