Substitution doesn't work for this, but elimination does.
-6x-8y=-20 +6( x+6y=-6)
-6x-8y=-20 + 6x+36y=-36
-6x and 6x cancel each other, add -8 and 36 to get 28, and -20 and -36 to get -56.
28y=-56
divide by 28 on both sides.
Y= -2
Then substitute y into one of the equations.
x+6(-2)=-6
x-12=-6
x=6
The ordered pair is (6,-2).