I like to solve these by graphing, so if you graph both of these functions (as shown in the picture below), you look for the intersection between the two graphs, which in this case is (-2,6).
You have 3x+2(-3x)=6. First you multiply using distributive property. Your new equation is 3x+-6x=6. Next you would add 3x+-6x, giving you -3x. now you have -3x=6. Lastly you would divide 6 by -3. This will give you that x is equal to -2.
