Since you're given the base for the perimeter of the rectangle, you can solve this question quickly.
First, you multiply 21 by 2, because there are two bases to a rectangle.
You'll get 42, and you will have to do 60-42 to find the perimeter for the remaining two sides.
60-42 will give you 18, so you can divide that by 2 because there are two other sides, giving you 9.
Now you have the side lengths 21 and 9. Area is base*height, so you can multiply 21*9 and get 189.
Therefore, the area of the rectangle is 189 meters