The first thing you want to do in this equation is get rid of the parenthesis. Because 4-2 is added to (3b+6) you cannot distribute the 2. However, there is an invisible 1 next to the parenthesis, so you can use that. Additionally, I like to change subtraction to addition of a negative number. It makes things a little less confusing.
4+ -2 + 3b + 6
Now just combine the like terms.
4 + -2 = 2
6+ 2 = 8
So the simplified version of your problem is: 3b + 8
