Question 190904
Suppose the polygon has n sides

The sum of the measures of the interior angles of a n-gon is {{{180(n-2)}}}.

As all angles of a regular polygon are equal in measure, the measure of each angle is:
{{{180(n-2)/n}}}

Setting it equal to 160, we have
{{{180(n-2)/n=160}}}
Solving for n, we have
{{{180(n-2)=160n}}}
{{{180n - 360 = 160n}}}
{{{20n = 360}}}
n = 18
So it is a 18-gon