(1)  First, in any isosceles triangle, the base (the third side, in your terminology) "is less than twice the length of either side".


     Without it, such a triangle CAN NOT EXIST.


     So, the cited condition IS NOT specific and DOES NOT specify any isosceles triangle.


     It is simply a necessary condition for EXISTING such a triangle.



(2)  Second, with the given condition, the problem HAS NO a unique solution,

     and the problem's question HAS NO a unique answer.



(3)  It is clear that this problem came NOT from any school textbook --- hence, it is created by some "composer".



(4)  DIAGNOSIS:  - the posted "problem" is a FAKE,  and 

                 - the person who created it, DOES NOT know Geometry,  and

                 - the source from which you recovered this problem, is UNTRUSTED (it is the most polite definition).

Your post seems to missing info.!! 

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