The perimeter of an isosceles triangle is 80cm, the base is 7cm less than the lateral side, find the sides of this triangle.

In order to find the sides of an isosceles triangle, we will compose and solve an equation.

But first of all we have to introduce a variable.

In the condition, we are given the perimeter of an isosceles triangle – 80 cm.And it is also known that the base is 7 cm less than the lateral side.

Let us denote the base of the triangle as x cm, then we write the lateral side as (x + 7) cm.

Perimeter of an isosceles triangle:

P = 2a + b;

a – side, b – base.

2 (x + 7) + x = 80;

2x + 14 + x = 80;

3x = 80 – 14;

3x = 66;

x = 66: 3;

x = 22 cm base of the triangle, then 22 + 7 = 29 cm side.