Task: Question Answering
Input (English): Problem: the number of diagonals of a polygon of n sides is given by the formula v = n ( n - 3 ) / 2 . if a polygon has twice as many diagonals as sides , how many sides does it have ? 
Options: a ) 3 , b ) 5 , c ) 6 , d ) 7 , e ) 8
Output (English): b