The perimeter of the square is more than 26 cm, but less than 30 cm. Estimate the length of the side of the square

First of all, let’s remember by what formula the perimeter of the square is determined:

P = 4 * a,

where P is the perimeter of the square,
a is the length of the side of the square.

Then, taking into account this equality, we can write the condition of the presented problem in the form of a double inequality:

26 cm <P <30 cm;
26 cm <4 * a <30 cm.

We divide all components of the double inequality by 4:

(26: 4) cm <a <(30: 4) cm,
6.5 cm <a <7.5 cm.

The length of the side of the square is within these limits. If it is expressed as an integer, then a = 7 cm.