The answer is b. 11.
You can find this by multiplying the two parenthesis together. In order to do this, you can use a multiplying process known as FOIL (First, Outer, Inner, Last), where you multiply parts of the parenthesis in this order to make sure you do so properly.
First Numbers:
2x * x = 2x^2
Outer Numbers:
2x * 6 = 12x
Inner Numbers:
-1 * x = -1x
Last Numbers:
-1*6 = -6
Now place them all in that order and simplify.
2x^2 + 12x - x - 6 ---> simplify x terms
2x^2 + 11x - 6
Since the middle term (the one with the x value) has a coefficient of 11, that gives us a b value of 11.
