x=6y+2

Question

3x-18y=4

Answer 1

sub the first into the 2nd ...

3x - 18y = 4
3(6y+2) - 18y = 4
18y + 6 - 18y = 4
6 = 4 , which of course is nonsese, so ..

there is no solution

(You have two parallel lines)