4x+18=7x-12
We move all terms to the left:
4x+18-(7x-12)=0
We get rid of parentheses
4x-7x+12+18=0
We add all the numbers together, and all the variables
-3x+30=0
We move all terms containing x to the left, all other terms to the right
-3x=-30
x=-30/-3
x=+10
Hope this helps :)