Let's solve for xx:
-x-3y = 15−x−3y=15
-x = 15+3y−x=15+3y
x = -15-3yx=−15−3y
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅
Now let's substitute that into the second equation
2(-15-3y) + 7y = -362(−15−3y)+7y=−36
-30 - 6y + 7y = -36−30−6y+7y=−36
-6y + 7y = -6−6y+7y=−6
y = -6y=−6
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅
Now we need to solve for xx:
x = -15-3(-6)x=−15−3(−6)
x = -15 + 18x=−15+18
x = 3x=3
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅
We should still check our work:
Plug in 33 for xx and -6−6 for yy
-(3) - 3(-6) −(3)−3(−6) should equal 1515
-3 - (-18)−3−(−18)
-3+18 = 15−3+18=15
15 = 1515=15, so we were right!!!
