Using the sum of interior angles equation;
(n-2)180=sum
(n-2)180=2340
n-2=2340/180
n-2=13.5
n=13.5+2
n=15.5
However, the problem is that a polygon cannot have "half" as side. Therefore, there might be a problem in the question or there is no solution to such a question.
Hope I helped :)