Question 428643
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Hi
1200 pupils in a secondary school
Let x and (1200-x)represent the number of girls and boys respectively
Question Set Up the Proportion***

{{{ 5/7 = x/(1200-x)}}}   | Cross Multiplying 
 7x = 5(1200-x)
 12x = 6000
  x =  500, the number of girls. the number of boys is 700  (1200-500)

CHECKING our Answer***
  5/7 = 500/700