Answer:
A. The value of x is 5
B. The length of each side is 20!
Step-by-step explanation:
For part A., We can determine x by setting these equations to equal each other (as we know that all sides of a square are equal)! See below for how to:

For part B. sub x for 5 to get the side length of one side...

We already know that all sides are equal, so the side length of each side is 20!
<em>Hope I was of assistance!</em> <em><u>#SpreadTheLove <3</u></em>