Task: Question Answering
Input (English): Problem: the perimeter of an equilateral triangle is 60 . if one of the sides of the equilateral triangle is the side of an isosceles triangle of perimeter 55 , then how long is the base of isosceles triangle ? 
Options: a ) 5 , b ) 10 , c ) 15 , d ) 20 , e ) 25
Output (English): c