We have the functions:
[tex]3x+6y=-18[/tex]And:
[tex]2y=3x-22\Rightarrow22=3x-2y[/tex]Knwoing this, we proceed as follows:
When we sustract the second function, from the first, we will have:
[tex]3x-3x-2y-6y=22+18\Rightarrow-8y=40[/tex][tex]\Rightarrow8y=-40\Rightarrow y=-5[/tex]If we replace in the first function we will get x = 4.
Where did you get the -3 and -36 from?