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The two lines are intersecting at the points x = 7, y = 3
Hence, the number of boys is 7 and the number of girls is 3

Example: (Substitution Method)

Now, Ravi is three times as old as Sourav. Five years later, Ravi will be two and a half
times as old as Sourav. How old are Ravi and Sourav now?

Solution: Let the age of Ravi be x years and the age of Sourav be y years (Now)
According to given condition
x = 3y (i)
and after 5 years , Ravi will be (x+5)years and the age of Sourav be (y+5) years

A/Q (x + 5) =
2x + 10 = 5y + 25
2x - 5y = 15 (ii)

Substituting x in eq.2

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