You go to the mall to buy some new shoes. You have a coupon for [tex]$\$[/tex]25[tex]$ off the price of a pair of shoes. When you arrive at the store, you find out that the shoes are on sale for $[/tex]25\%[tex]$ off.

If $[/tex]c(x)=x-25[tex]$ represents the cost of the shoes with your coupon and $[/tex]s(x)=0.75x[tex]$ is the cost of shoes after the markdown, which of the following composition functions represents using the coupon and then receiving the markdown?

A. $[/tex]c(s(x))=0.75x-25[tex]$
B. $[/tex]c(s(x))=0.75x-18.75[tex]$
C. $[/tex]s(c(x))=0.75x-18.75[tex]$
D. $[/tex]s(c(x))=0.75x-25$



Answer :

To solve this problem, we need to determine the correct composition function that represents using the coupon and then receiving the markdown.

1. Understanding the Functions:
- [tex]\( c(x) = x - 25 \)[/tex]: This represents the cost of the shoes after applying the \$25 coupon.
- [tex]\( s(x) = 0.75x \)[/tex]: This represents the cost of the shoes after a [tex]\(25\%\)[/tex] markdown.

2. Applying the Coupon First, Then the Markdown:
To find the composition function representing using the coupon first and then applying the markdown, we need to apply the markdown function [tex]\( s(x) \)[/tex] to the cost after the coupon function [tex]\( c(x) \)[/tex].

3. Step-by-Step Composition:
- Start by applying the coupon [tex]\( c(x) = x - 25 \)[/tex] to the original price [tex]\( x \)[/tex].
[tex]\[ \text{New price after coupon is } c(x) = x - 25. \][/tex]
- Next, apply the markdown [tex]\( s(x) = 0.75x \)[/tex] to the result [tex]\( (x - 25) \)[/tex].
[tex]\[ s(c(x)) = 0.75(x - 25). \][/tex]

4. Simplify the Composition:
- Distribute the [tex]\( 0.75 \)[/tex] inside the parentheses:
[tex]\[ s(c(x)) = 0.75 \cdot x - 0.75 \cdot 25. \][/tex]
- Calculate [tex]\( 0.75 \times 25 \)[/tex]:
[tex]\[ 0.75 \cdot 25 = 18.75. \][/tex]
- Therefore, the expression simplifies to:
[tex]\[ s(c(x)) = 0.75x - 18.75. \][/tex]

Thus, the composition function that represents using the coupon first and then receiving the markdown is:
[tex]\[ s(c(x)) = 0.75x - 18.75. \][/tex]

Final Answer:
[tex]\[ \boxed{s(c(x)) = 0.75x - 18.75} \][/tex]