Answer:
1)

2)

3)

4)

Explanation:
1) By definition, a pentagon is a polygon which has five sides and five vertices.
2) The perimeter of a pentagon can be calculated by adding the lenght of its sides. Therefore you can write the following expression:

3) Or you can calculated by multiplying the lenght of one side by 5:

4) You can also write it in this form:

5) Or simplified:
