The exterior angle of a regular polygon is 18°. what is the sum of its interior angles.

An interior angle = 180-18 = 162
let n be the no. of sides of the polygon
(n-2)*180/n=162
180n-360=162n
18n=360
n=20
sum of its interior angles= (20-2)*180 =3240

20 sides.

Number of sides = 360/ measure of exterior angle

= 360/18

= 20 sides.

Sum of interior angles = 180*(n-2)

= 180 * (20-2)

= 180 * 18

= 3240
I hope that helped