4/20 = x/20 +x
80 + 4x = 20x
80/16 = x
5 = x
that being said. Is that your name???
Answer: 
Step-by-step explanation:
You need to analize the information given in the exercise.
In this case you know that the List price is:

And, based on the data given, you also know that the Trade discount is:

Then, the first step you need to apply is to multiply the List price by the Trade discount, as you can observe below:

Now it is important to remember that, by definition, the Net cost can be found by subtracting the List price (which in this case is $74.13) and the product of the List price and the Trade discount (which in this case is $24.71).
Then, through this procedure, you get the following Net cost:

Simplify the following:
((-1^3)/(-3)^(-3))^2
1^3 = 1:
((-1)/(-3)^(-3))^2
(-3)^(-3) = 1/(-1)^3×1/3^3 = (-1)/3^3:
((-1)/((-1)/3^3))^2
3^3 = 3×3^2:
((-1)/(-1/(3×3^2)))^2
3^2 = 9:
((-1)/((-1)/(3×9)))^2
3×9 = 27:
((-1)/((-1)/27))^2
Multiply the numerator of (-1)/((-1)/27) by the reciprocal of the denominator. (-1)/((-1)/27) = (-27)/(-1):
((-27)/(-1))^2
(-27)/(-1) = (-1)/(-1)×27 = 27:
27^2
| 2 | 7
× | 2 | 7
1 | 8 | 9
5 | 4 | 0
7 | 2 | 9:
Answer: 729 = 1/729 thus c: is your Answer