ANSWER:

SEMI - perimeter of TRIANGLE is 33 cm.

Explanation:

Hello user

◤Given that:

• The length of the first side is 5 cm less than the length of the second side.

• The length of the THIRD side is 7 cm more than the length of the first side if the first side is of length is 18 cm.

To find:

• the semiperimeter of the triangle.

Formula to know:-

Semi- perimeter (s) = (a+b+c)/2

Solution:☈

Length of the first side is 5cm less then the length of the second side.

Length of the first side = Length of second side - 5cm

It is given that the length of the first side is 18 cm.

18 cm = Length of the second side - 5cm

Length of second side = 18 cm + 5 cm

Length of second side = 23 cm.

Length of the third side is 7 cm more than length of the first side.

Length of the third side = 7cm + length of first side

Length of third side = 7 cm + 8 cm

Length of third side = 25 cm.

Let the side a = 18 cm

Let the side b = 23 cm

Let the side c = 25 cm

Semi - perimeter (s) = (a+b+c)/2

S = (18 cm + 23 cm + 25 cm)/2

S = (66 cm)/2

S = 33 cm.

Semi - perimeter of triangle = 33 cm. Ans