SOLVE THE EQUATION

y = x + 6

I am pretty sure your text does not say

"solve the equation y = x+6 "

There is no unique "solution" to this equation of a straight line, since each point on the line would be a solution, and the number of such points would be infinite.

Here are just 3 of those infinite number of solutions:
(0,6), (1,7), (34.5 , 40.5)