Question

Y = -x + 12
y = -x + 20

Answer 1

since both are equal to y, set both equations equal to each other

-x + 12 = -x + 20

now, subtract 12 from both sides

-x = -x + 8

now, add the x that was previously on the the side with the 8

-x = -x + 8
+x +x

0 = 8 since this is false, the answer is no solution

hoped this helped!