Answer: b = -3
Explanation:
First you use distribution to solve 2(b+12). 
2 x b = 2b and 2 x 12 = 24 
So you've got 2b + 24.
Then, you put the entire equation together
2b + 24 +4b = 6 
You combine like terms: 2b + 4b = 6b 
So, 6b + 24 = 6 
Subtract 6 - 24; since you're trying to get both the variable and number on opposite sides of each other. 
Therefore, 6b/6 = -18/6; Divde 6 by both sides
That gives you b = - 3