how do i isolate x when doing substitution method if x is on both sides?

Question

question:

15x -18-2y = -3x +y

10x+7y+20 = 4x+2

 

Using the substitution method, how do I work this out? I cant even isolate x.

Answer 1

15x - 18 -2y = -3x + y

18x - 18 -2y = y                    add 3x to both sides

18x - 18 = 3y                        add 2y to both sides

18x = 3y + 18                       add 18 to both sides

x = 1/6y + 1                          divide by 18 on both sides

Answer 2

10x + 7y +20 = 4x + 2

6x +7y +20 = 2                                subtract 4x from both sides

6x + 20  = -7y +2                             subtract 7y from both sides

6x = -7y -18                                     subtract 20 from both sides

x = -7/6y - 3                                     divide by 6 on both sides