Question

How do you solve this by substitution?
x=6y+2
3x-18y=4


This is the answer I get:
3(6y+2)-18y=4
18y+6-18y=4
18y+1818y+6-18y+18y=4
36y=10
36 36
Y=5/18

3x-18(5/18) =4
3x-5+5= 4+5
3x= 9
3 3
X=3
(3, 5/18)

Answer 1

If you rearrange things a bit, you get

x - 6y = 2
3x - 18y = 4

which is the same as

x - 6y = 2
x - 6y = 4/3

The lines are parallel, so there is no intersection, and no solution to the equations.

Your answer fits the 2nd equation, but not the first.