Length 40mm perimeter 22 cm, find the width and area?

Determine the width of the rectangle, provided that its perimeter is 22 cm and the length = 40 mm or 4 cm, based on the fact that 1 cm = 10 mm.
Let’s remember the formula for determining the sum of all sides of such a figure:

P = 2a + 2b.

Let’s create an equation by substituting the known values:

2 * 4 + 2b = 22.

We will leave the unknown on the left side of the equation, and transfer the number to the right, changing the sign in front of it to the opposite:

2b = 22 – 8 = 14.

The second factor is the quotient of the first:

b = 14: 2 = 7 cm.

The area of the rectangle is calculated by the formula:
S = a * b = 4 * 7 = 28 cm.