Question 1193567
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The sum of interior angles of a n-gon is  180*(n-2) degrees.


In your case, equation for unknown number of sides (of vertices) is

    180*(n-2) = 540  degrees.


Divide both sides by 180

    n-2 = 540/180 = 3

     n            = 3 + 2.


<U>ANSWER</U>.  n = 5:  your polygon is a pentagon.
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Solved.