There were an equal number of girls in Class B and Class C. ³₄ of the students in Class B and ¹₆ of the students in Class C are boys. If there are 28 more boys in Class B than in Class C, what is the total number of students in Class B and Class C?
Fraction of the students in Class B that are girls
= 1 - ³₄
=  ¹₄

Fraction of the students in Class C that are girls
= 1 - ¹₆
= ⁵₆ 

The number of girls in Class B is equal to the number of girls in Class C. LCM of 1 and 5 is 5. Make the numerators the same. 

 1x54x5 Class B = 56 Class C 
 520 Class B = 56 Class C

Number of girls in each class = 5 u

Total number of students in Class B = 20 u
Total number of students in Class C = 6 u

Number of boys in Class B
= 20 u - 5 u
= 15 u

Number of boys in Class C
= 6 u - 5 u
= 1 u

Number of more boys in Class B than Class C
= 15 u - 1 u
= 14 u

14 u = 28

1 u = 28 ÷ 14 = 2

Total number of students
= 20 u + 6 u
= 26 u
= 26 x 2
= 52

Answer(s): 52