First choice is volume or surface area, second is less or greater, and last is add or subtract.

1: surface area 2: greater 3: add

Step-by-step explanation:

You can't say what that is without knowing what a and b are. Did the question ask what the coefficient of a is? A coefficient is just the normal number that doesn't change (like 7) that is multiplied by a variable (like x). So the coefficient of 6a is 6. Also, b is the same as 1b so the coefficient of b is 1