solve by the substitution method
5x+7y=6
-6x+y=21
from the 2nd ---> y = 21 + 6x
plug that into the 1st
5x + 7(21+6x) = 6 solve for x, then sub back into
y = 21+6x
5x+7y=6
-6x+y=21
plug that into the 1st
5x + 7(21+6x) = 6 solve for x, then sub back into
y = 21+6x