Question

solving with substitution
x+y=11
-x=-y-9

Answer 1

easier if you write the second equation as
\[x=y+9\] then substitute in the first to get
\[y+9+y=11\]
\[2x+9=11\]
\[2y=2\]
\[y=1\]

Answer 2

x+y=11
-x=-y-9 --> x = y+9
y+9+y=11
2y=2
y=1
x=10

Answer 3

x+y=11....(1)
-x=-y-9....(2)

from (2) you get x=y+9
in (1) y+9+y=11
2y=2
y=1
x=1+9
x=10

Answer 4

satellite meant \[2y+9=11\] on his second line. But the answer remains the same :)