Question

Solve the following equations by substitution method 

i) 2x – 7y = 3 

ii) 4x + y = 21

Answer 1

The given two linear equations are 

2x – 7y = 3 …………. (1) 

4x + y = 21 …………..(2) 

From the equation (2) we get 

y = 21 – 4x now we substitute this Y 

value in equation (1) 

We get 

2x – 7(21 – 4x) = 3 

⇒ 2x- 147 + 28 x – 3 

⇒ 30 x = 147 + 3 = 150 

then x = 150/30 ∴ x = 5

 Now put x = 5 in equation (2) we get 

4(5) + y = 21 

20 + y = 21 

y = 21 – 20 = 1 

So x = 5 and y = 1 are the solutions of the system.