Answer:
9
Explanation:
The sum of the interior angles of a polygon is
sum = 180° (n - 2) ← n is the number of sides, thus
180 (n - 2) = 1260 ( divide both sides by 180 )
n - 2 = 7 ( add 2 to both sides )
n = 9
The number of sides of the regular polygon is 9