Answer :

6x +30 -3x +6 =12x +18

3x +36 =12x +18

3x-12x = 18 -36

-9x = -18  | -1

9x =18

x= 18/9

x=2
[tex]6(x+5)-3(x-2)=12x+18\\\\6\times x+6\times5-3\times x-3\times(-2)=12x+18\\\\6x+30-3x+6=12x+18\\\\3x+36=12x+18\ \ \ \ \ |subtract\ 36\ from\ both\ sides\\\\3x=12x-18\ \ \ \ |subract\ 12x\ from\ both\ sides\\\\-9x=-18\ \ \ \ \ |divide\ both\ sides\ by\ (-9)\\\\\boxed{x=2}[/tex]