There are a variety of modern definitions of economics, some reflect evolving views of the subject or different views among economists.
So the area of the square is 7 x7 = 49 cm^2 and the perimeter of the square is 7 x 4 = 28 cm. And in example 1 you have a square of side length 8cm and you need to work out the area and perimeter of the square. So the area of the square is 8 x8 = 64 cm^2 and the perimeter of the square is 8 x 4 = 32 cm.
Area is defined as the number of square units that covers a closed figure. In the example shown, the area of the yellow square is 16 square units. That means, 16 square units are needed to cover the surface enclosed by the square. Formulas are defined to calculate the area of regular geometric figures like square, rectangle, circle, etc.