Question 1053556
Let w be the width of the rectangle. Then the length of the rectangle is 2w+10. So:
w(2w+10)=48
2w²+10w-48=0
w²+5w-24=0
(w+8)(w-3)=0
w=3 or -8. 
Throwing out the negative result, we get the width to be 3 ft., and the length to be 16 ft. ☺☺☺☺.