The difference of semi-perimeter and the sides of △ABC are 8, 7 and 5 cm respectively. Its semi-perimeter ‘s’ is

The problem states that the differences between the semi-perimeter and the sides of the triangle are 8, 7, and 5 cm. We can use this information to set up equations and solve for the semi-perimeter.

Let's denote the sides of the triangle as a, b, and c. The semi-perimeter (s) of a triangle is calculated as (a + b + c) / 2.

According to the problem, we have:

s - a = 8, s - b = 7, s - c = 5.

We can add these three equations together to get:

3s - (a + b + c) = 20.

But we know that 2s = a + b + c (from the formula of the semi-perimeter), so we can substitute this into the equation to get:

3s - 2s = 20, which simplifies to s = 20 cm.

So, the semi-perimeter of the triangle is 20 cm.