Find the sides of an equilateral triangle if its perimeter is 31 cm, and the base is shorter than the side by 2.6 cm.

An isosceles triangle is a triangle in which the two sides are equal.

1) Let x cm be the length of the side of the triangle.

2) Then (x – 2.6) cm is the base of this triangle.

3) The perimeter of a triangle is equal to the sum of the lengths of all its sides:

(x + x + (x – 2.6)) cm.

4) By the condition of the problem, the perimeter of this triangle is 31 cm.

Let’s compose and solve the equation:

x + x + (x – 2.6) = 31;

3x – 2.6 = 31;

3x = 31 + 2.6;

3x = 33.6;

x = 33.6: 3;

x = 11.2.

5) x = 11.2 cm – lateral side.

6) 11.2 – 2.6 = 8.6 cm – base.

Answer: 11.2, 11.2 and 8.6 cm.