There were an equal number of boys in Class B and Class C. ⁵₆ of the pupils in Class B and ¹₄ of the pupils in Class C are girls. If there are 28 more girls in Class B than in Class C, what is the total number of pupils in Class B and Class C?
Fraction of the pupils in Class B that are boys
= 1 - ⁵₆
=  ¹₆

Fraction of the pupils in Class C that are boys
= 1 - ¹₄
= ³₄ 

The number of boys in Class B is equal to the number of boys in Class C. LCM of 1 and 3 is 3. Make the numerators the same. 

 1x36x3 Class B = 34 Class C 
 318 Class B = 34 Class C

Number of boys in each class = 3 u

Total number of pupils in Class B = 18 u
Total number of pupils in Class C = 4 u

Number of girls in Class B
= 18 u - 3 u
= 15 u

Number of girls in Class C
= 4 u - 3 u
= 1 u

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

14 u = 28

1 u = 28 ÷ 14 = 2

Total number of pupils
= 18 u + 4 u
= 22 u
= 22 x 2
= 44

Answer(s): 44