Math help please, ten points

Solve the system of linear equations by subsitution.

x - 2y = 9

x - y = 11

x - y = 11
x = y + 11

(y + 11) - 2y = 9
-y = -2
y = 2

x - 2 = 11
x = 13

CHECK

13 - 2(2) = 9


(13, 2)

solve for one variable in the easier problem.

#2 : x =y +11

substitue in the first problem.

#1 : (y+11) - 2y = 9

solve for y

plug the y into BOTH equations to solve for x.
if the answers are the same both x and y are correct

muliply bortom line by 2( everything on it) then cancel the y's. 2x is 20. x is 10. sub 19 in for x in one of equaions. 10 - y is 11. y is 11 - 10. y is 1

x=2y+9

so

2y+9 -y=11
y+9 =11
y=2

plug that into first equation:

x-2(2)=9
x-4=9
x=13

(13, 2)

x-y=11 --> y=11-x --> x-2(11-x)=9 --> x-22-2x=9 -->-x=-13 --> x=13

If x=13 then
13-2y=9 -->-2y=-4 y=2

Answers:
x=13
y=2