Question

name one angle in a regular 9-gon.

Answer 1

Do you mean tell how many degrees in each interior angle of a regular 9-g0n?

Answer 2

yes

Answer 3

There's 7 triangles in 9-gon, each triangle's interior angles sum is 180
Thus, a 9-gon's interior angle sum is 7* 180 = 1260 degrees

We want to know how many degrees there are in each interior angle, since a 9-gon has 9 interior angles, 1260/9 = 140 degrees.