What is the area of 11 m 21 m 8 m 5 m
Here's how to find the area of an irregular polygon.
http://www.mathopenref.com/polygonirregulararea.html
And, to make things worse, just having the side length does not determine the area. Take a square. It can be squashed flat, giving area from s^2 down to 0.
To find the area of a rectangular shape, you need to multiply the length by the width.
In this case, the given measurements are 11 m, 21 m, 8 m, and 5 m. However, it is unclear which two measurements are the length and the width. To calculate the area, we need to know which sides correspond to length and width.
Once you determine which sides are the length and the width, multiply those measurements together. For example, if 11 m is the length and 21 m is the width, you would calculate the area as follows:
Area = Length x Width
Area = 11 m x 21 m
Area = 231 m²