Question

Ok, I tried watching a video on how to solve a system by substitution. But I feel like I did it wrong, so can someone check my work and show/ tell me where I went wrong.

So the system by substitution
-2x-3y=-2
Y=2x+6

First I combined my 2 equations but without y so I’d have 1 equation
-2x-3(2x+6)=-2
Then I multiplied 3 with 2 and 6 and got
-2x-6x+18=-2
Then added -2 and 6 and got
-8x+18=-2
(Then I did some more stuff the man in the video did)
-8x+18=-2
-18-18
And I ended up with this -8/8x=-16/18=-8/9
Meanwhile the man in the video I guess did his correctly and found his x mean while I’m confused and lost. So can someone help me?...

Answer 1

Your error is in this line: -2x-6x+18=-2
should have been -18, since (-3)(+6) = -18

so ..
-2x-6x-18=-2
-8x - 18 = -2
-8x = 18-2
-8x = 16
x = -2

sub back into y = 2x+6
= 2(-2) + 6
= 2

x = -2, y = 2