For f(x) to be a function, the value of x should not be repeated. That is no x value can be more then once.
So the required table is

And for g(x) , not to be a function, we have to repeat x value that is

Answer:
The answer to your question is $21.0
Step-by-step explanation:
Data
Original price = $25
Discount = 20%
Taxes = 5%
Process
1.- Calculate the price with the discount
$25 ------------------- 100%
x ------------------- 20%
x = (20 x 25) / 100
x = 500 / 100
x = $5
Price after the discount = $25 - $5
= $20
2.- Calculate the price after taxes
$20 ---------------------- 100%
x ----------------------- 5%
x = (5 x 20) / 100
x = 100 / 100
x = $1
Final price = $20 + $1
= $21
In short, (h o g)(a) is just h( g(a) ).
so what we can do is simply get g(a) first and then plug that in h(x).
The circumference of a circle is equal to the diameter times pi. So, let's look at what happens if you double the radius of a circle -- say from 2 to 4. The area will go from 12.56 to 50.24. This means that it has quadrupled.