Question 21031
Remember that the sum of the interior angles of a polygon is given by:
{{{S = (n-2)180}}} Where S = the sum of the angles (1260 degrees in this case) and n = the number of sides of the polygon.

{{{1260 = (n-2)180}}} Divide both sides by 180.
{{{7 = n-2}}} Add 2 to both sides.
{{{n = 9}}}

The polygon has 9 sides.