Answer :

x - width
x+6 - length

[tex]x(x+6)=55\\ x^2+6x-55=0\\ x^2+11x-5x-55=0\\ x(x+11)-5(x+11)=0\\ (x-5)(x+11)=0\\ x=5 \vee x=-11 [/tex]

x=5 feet
x+6=11 feet