Calculate the area of a square that has the same perimeter as a rectangle with sides of 5 cm and 7 cm.

In order to calculate the area of a square, the perimeter of which is equal to a rectangle with sides of 5 and 7 cm, first of all we find it by the formula: P = 2a + 2b, since the rectangle has 4 sides, opposite of which are equal.
P = 2 * 5 + 2 * 7 = 10 + 14 = 24 cm.
Since the perimeter of the square is also equal to this value, with equal sides, we find their value by composing the equation:
4a = 24,
a = 24: 4 = 6 cm.
S square: a² = 6² = 36 cm².