Cozy Closet children's store is having its annual winter sale, during which every item in the store is marked down. Pajama sets sell for $7 less than the full price during the sale. Mr. Dorsey purchases 3 matching pajama sets, one for each of his children, and pays a total of $57.

Which equation can you use to find how much money, [tex] f [/tex], each pajama set costs at full price?

A. [tex] 7(f-3)=57 [/tex]

B. [tex] 3(f-7)=57 [/tex]

C. [tex] 3f-7=57 [/tex]

D. [tex] 7f-3=57 [/tex]

Let the full price of each pajama set be [tex]$f$[/tex]. During the sale, each set is sold for [tex]$7$[/tex] dollars less than the full price. Therefore, the sale price for one set is

[tex]$$f - 7.$$[/tex]

Since Mr. Dorsey bought 3 sets and paid a total of \[tex]$57, we can write the total cost as

$[/tex][tex]$3(f-7)=57.$[/tex][tex]$

Thus, the equation to find $[/tex]f[tex]$ is

$[/tex][tex]$\boxed{3(f-7)=57.}$[/tex][tex]$

Now, solving for $[/tex]f[tex]$ step-by-step:

1. Divide both sides of the equation by 3:

$[/tex][tex]$f - 7 = \frac{57}{3} = 19.$[/tex][tex]$

2. Add 7 to both sides:

$[/tex][tex]$f = 19 + 7 = 26.$[/tex][tex]$

So, each pajama set costs \$[/tex]26 at full price. The correct equation is

[tex]$$3(f-7)=57.$$[/tex]