Answer:
16.3333333 is the correct answer.
Yeah. You basically have to look at every x value and see if for every x value, is there ONLY one y-value. So in your example, it is a function because every x value has only one y value. Let’s say you had (1,3) and (1,5). That would not be a function because the x value of 1 has TWO y values (3 and 5), therefore it is not a function.
That’s how you can easily spot if something is a function by just looking at a handful of ordered pairs. I hope this makes sense.
Explanation
The question requires that we figure out the sides that represent the top/bottom faces and the left/right faces.
We are given the plan of the aluminum sheet
The top, bottom, left and right faces are shown below
The dimension for the top and bottom is

Since they are two
Therefore the total area for the top and bottom will be

For the left and right faces, the dimensions are
The dimensions of the left and right faces will be

Since they are two, then
The area will be