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.
The base of the triangle is equal to a side of the square, which is 8 cm. You can use these numbers to determine the area. A of square = s ^2 = 8^ = 64 cm^2. A of triangle = (1/2) * b * h = (1/2)* 8 * 2 = 8 cm^2. Then you just add the areas together to get the total area of the figure. A = 64 + 8 = 72 cm^2.