Answer:
441
Step-by-step explanation:
If this is a rectangle, meaning the width and the legnth is different, there is no way in solving this.
However, if it is a square, meaning all the sides are the same,
we can know that every side is 21 inches long.
An area is the width times the length, which is both 21 in this case.
21 times 21 = 441.
441 inches squared.