Answer :

lets use width=w and length=l
we know that 2w+2l = 56, and that 6l=1w
since the second equation is already solved for w, we can plug that into the first equation, giving 2(6l)+2l=56.
solving for l will give us 12l+2l=56 => 14l=56 => l=56/14=4
with l=4, we can find the width using the second equation. 
6(4)=w
w=24
Final answer:
The length is 4 inches and the width is 24 inches.
Hope I helped :)