The perimeter of a triangle is 28ft. the medium side is 4ft longer than the shortest side, while the longest side is twice as long as the shortest side. what are the lengths of the three sides?

28= a+b+c                           The shortest side is 6ft, the medium side is 10ft, and 
28= (a)+(a+4)+(2a)                the longest side is 12ft.
28= 2a+4+2a
28= 4a+4
24= 4a
a=6
b= 6+4
b= 10
c= (2)(6)
c= 12