Question

number of sides, a regular polygon has if each of its enterior angle is 108 degree

Answer 1

each interior angle is 108 degree which means each exterior angle will be 180 - 108 degree= 72°
now number of sight
360°/72= 5
number of sides equal to 5 which means it is a regular pentagon

Answer 2

180×(n-2)/n=108
or, n-2=.6n
or, n= 2/.4
or, n=5
so number of sides is 5.