Find the side length of a square whose perimeter is equal to the perimeter of a rectangle with sides of 7cm and 5cm.

Let’s find what the perimeter of a rectangle with sides of 7 cm and 5 cm is equal to.
Since the perimeter of any rectangle is equal to twice the sum of the length and width of this rectangle, then the perimeter P of this rectangle is:
P = 2 * (7 + 5) = 2 * 12 = 24 cm.
Find the side length of a square whose perimeter is equal to the perimeter of this rectangle.
Let us denote the length of the side of the square by x.
Since the perimeter of this rectangle is 24 cm, and the perimeter of any square is equal to the side of the square multiplied by 4, we can write the following equation:
4 * x = 24.
We solve the resulting equation:
x = 24/4;
x = 6 cm.
Answer: the length of the side of the square is 6 cm.