It's easy. Just combine like terms. Like terms must have the same variable and to the same power in this case all the terms have a power of 1, but it doesnt show it because it doesn't really matter. So 4x,6x, and 2x all have the same variable so add them together. That gets you 10x. Since nothing else in the expression has the same variable with 10, you leave the 10 at the end resolving in 12x+10
