Answer:
9m
Explanation:
To find the width of a rectangle given area and length all you need to do is take your area (189 in this case) and divide it by your length. (In this case 21.)
Here's our equation:
189 ÷ 21 = 9
(remember the meters squared is important if you're finding area. This doesn't apply in our case as we're only finding the width. To be more clear the "m² and/or m^2")
9m is your answer.
Hope this helps and have a nice day!