



 
Hi, I can help get you started. Look at one of the vertices $V$ where the internal angle measures $140^{0}.$ The external angle then measures $180^0  140^0 = 40^{0}.$ What is the measure of the external angle at a vertex where the internal angle measures $155^{0}?$ Now look at Walter's note about the sum of the measures of the external angles of a convex polygon. Write back if you need more assistance,  


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