Question

if a polygon have two interior angle of 90 degrees and the others are each 120 degrees then what is the number of sides of the polygon?

Answer 1

Fact: The exterior angles of a polygon add up to 360 degrees.
An exterior angle is 180-interior angle in degrees.

Let the polygon have n sides, then
2(180-90) + (n-2)(180-120) = 360
60(n-2)=360-180=180
n-2=3
n=5
So it is a pentagon