Question 1194175
The ratio of the interior angle to the exterior angle of a regular polygon is 5:2. Find the number of sides of the polygon 
---------
5 + 2 = 7
7 sides
=================
PS  That doesn't always work.
Here's the long version:
5x + 2x = 180
x = 180/7
Ext angles = 2x = 360/7
# of sides = 7.