Answer:
Part (A): The correct option is C) x + $9 = $21
Part (B): The correct option is B) $12
Explanation:
Consider the provided information.
Part (A)
Karen buys a picture frame on sale for $9.
A week later she buys the same frame for the regular price.
Let the regular price is x dollar.
The total price for the frames is $21.
Therefore the required equation is:

Hence, the correct option is C) x + $9 = $21
Part (B) Find the regular price.
Consider the equation

Solve the equation for x.


Hence, the regular price of the frame is $12.
Therefore, the correct option is B) $12