x - 2y = 6
3x - 6y = 18
It looks to me like substitution is the best method for solving this system. To do that, I can isolate x on the first equation and substitute its expression for x in the second equation:
x - 2y = 6
x = 2y + 6
Now substitute into the second equation:
3(2y + 6) = 18
6y + 6 = 18
6y = 12
y = 2
Substitute the value for y into the first equation to find x:
x - 2(2) = 6
x -4 = 6
x = 10
Finally, substitute both values into both original equations to check work:
10 - 2(2) = 6 --> 10 - 4 = 6 <--This is correct
3(10) - 6(2) = 18 --> 30 -12 = 18 <--This is correct
Hope this helps.