When you add 18 to 1/4 of a number, you get the number itself. The equation(s) that may be used to solve this problem is (let n = number):

n=24.

Step-by-step explanation:

1/4 of 24 is 6, and 6+18= 24.

Look at the attachment for the graph of part A. It's the one with 3 red points. :)

Part A)

Yes, the graph shows a linear function. You can see that the 3 points all have the same slope and form a linear line. It is also a function because it passes the vertical line test.

Part B)
Here is an example of a linear function:
y = 3x + 4
I have attached the graph of that also. It's the line that is red.
You can see that it is linear and also a function!

Here is an example of a non-linear function:
y = 3x^2 + 2
I have attached a graph of this one also. It's a blue parabola :P
You can see that it is not linear, but it is also a function.