This might look hard at first, but if you break it down into parts, it will be much easier. With that said, start with what you know. You see that the word problem says "the difference of y and 9", which means that you have to stubtract them. So, part of the equation is going to be y - 9. Now to look at the rest of the word problem. It says to divide by 3, so now you have to take what you have so far and divide that by 3. This means that you are going to have to divide the y - 9 by 3.
Your answer should be:
y - 9 / 3
***** Note: The slash means division. *************************************
First, square both sides. This will cancel out the radical.

(a^2 = b + 6)
Then subtract 6 from both sides
b = a^2 - 6
Cindy needs to buy 8 packs of invitations.
Domain is X and Range is Y. So the range will be all the Y's which is the second answer
Answer:
when added to the original number, would equate to zero. Another term this may be known as is the additive identity. The additive inverse is simply:
(a + bi) = -(a + bi)
Given: 9 - 4i
-(9 - 4i) = -9 + 4i
Therefore, the answer is B.