Question

solve the following simultaneous equation by substitution method x+y=7;2x-y=20​

Answer 1

Solution:

let eq. (1) be x+y= 7.and eq. (2) be 2x-y= 20

now in (1),

x+y= 7

x= 7-y.....(3)

substituting the value of x in (2),

2x-y= 20

2(7-y) -y=20

14-2y-y=20

14-3y=20

-3y=20-14

-3y=6

y=6/-3=-2

now,

substituting value of y in (3),

x=7-y

x=7+2

x=9

therefore,.

(x,y)=(9,-2,)

hope this helps!!☺❤✌

Answer 2

$x = 7 - y$

putting in second equation

$2(7 - y) - y = 20$

find y

$y = - 2$

put in 1st equation

$x = 7 - ( - 2)$

x=9