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Int - Ext = 108,
Int + Ext = 180
---------------------Add the two equations
2*Int = 108 + 180 = 288 ----> Int =
= 144.
Thus the Interior angle is 144 degs.
Then the Exterior angle is 180 - 144 = 36 degs.
For any convex polygon, the sum of its exterior angles is 360 degs.
Therefore, the number of sides of the polygon is
= 10.
Answer. n = 10: it is regular decagon.