Let's solve this by substitution. Note that y is defined: y = 2x - 2. Subst. 2x - 2 for y in the other equation: -6x + 3(2x - 2) = 18.
Then -6x + 6x - 6 = 18. Unfortunately, -6 does not equal 18, so there is no solution. The graphs of these two lines are parallel.