Not understanding this concept too well help would be appreciated.

Sean, this is an example of Defined Function questions. In this type of questions, the author will define a function using symbols such as @, *, etc. to confuse you.

But if you understand functions, you can rewrite it to understand it better. For example, a@b is a function involving the variables a and b, i.e., ƒ(a,b) =a^3 - 1. Since b does not really play a role, we can write it simply as a function of a, i.e., ƒ(a) = a^3 - 1. Hence x@1 = ƒ(x,1) = ƒ(x) = x^3 - 1.

I still don't understand! Do we have "@" symbol in Math?

Channy, in math you can invent symbols to define a function. In this exercise set the functions are represented by various symbols like @, *, etc. In particular this question, the symbol @ is used to represent the function. In standard notation, a function that operates on a variable x is written as f(x). A function that operates on the variables x and y is written as f(x,y).

If there's no b mentioned in the function, then the answer should be simple. The answer is (C).