Question

find the solution of the following by substitution method​

Answer 1

Solution:

Given

3x-y = 12 ---(1)

and

x+2y = 11

=> x= 11-2y ----(2)

Substitute (2) in equation (1) ,

we get

3(11-2y)-y = 12

=> 33-6y-y = 12

=> -7y = 12 - 33

=> -7y = -21

=> y = (-21)/(-7)

=> y = 3

Now ,

put y= 3 in equation (2), we get

x= 11-2×3

=> x = 11 - 6

=> x = 5

Therefore ,

x = 5 , y = 3

•••

Answer 2

$3x - y = 12............(1) \\ x + 2y = 11............(2) \\ x = 11 - 2y............(3) \\ put \: value \: of \: x \: in \: eq \: (1) \\ 3x - y = 12 \\ 3(11 - 2y) - y = 12 \\ 33 - 6y - y = 12 \\ 33 - 12 = 7y \\ 7y = 21 \\ y = \frac{21}{7} \\ y = 3 \\ put \: value \: of \: y \: in \: eq \: (3) \\ x = 11 - 2y \\ x = 11 - 2(3) \\ x = 11 - 6 \\ x = 5$