First, you combine like terms: x+3x=4x: 12+4x=18-2x
Second, you add the 2x to each side (inverse operation): 12+6x=18
Third, you subtract 12 from 18 to cancel out the 12 (inverse operation): 6x=6
Fourth, you divide each side by 6 to find the value of x
The answer is x=1