Answer:
A.

Explanation:
We are given that Sam is baking cakes at her parent;s bakery.
We have to write an equation to show how many cakes baked by Sam this week.
Let x be the number of cakes baked by Sam this week
If she gets paid for every cakes =$3
Then, she gets paid for x cakes=3x
According to question
Total money made by Sam on this week =20+3x
Substitute the values then we get

This is required equation to show how many cakes baked by Sam this week.
Hence, option A is true.