Chapter I : Linear Equations in two variables in two variables

Example 16. The sum of two digit number and the number obtained by reversing the order of its digit is 99. If the digits differ by 3, find the number.

Solution: Let the digit at unit's place be x and that at ten’s place be y .

Original number = 10y + x

Reversed number = 10x + y

Also,

When x - y = 3 ---------------- (2)

and x + y = 9

Adding we get 2x = 12