Question

If x+y=5 and 2x+3y=5, then find the value of x-y
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Answer 1

To find the value of x-y, first we need to find 'x' and 'y'.

GIVEN: A pair of linear equations in two variables:-

x + y = 5 -------> (1)

2x + 3y = 5 -------> (2)

LCM (2,1) = 2

Eqn (1) × 2 --> 2x + 2y= 10

Eqn (2) × 1 --> 2x + 3y = 5

Subtract ==> y = -5

Substitute y = -5 in Eqn (1),

I.e, x + (-5) = 5

--> x = 10

Since we have found the values of x and y, we can now find the value of x - y.

x - y = 10 - (-5) = 10 + 5 = 15

∴ x - y = 15

Note: I have solved the equations by Elimination Method. You can also use Substitution or Cross Multiplication Method... :)