Area= length * width
plug in the numbers known
9/20= L * 1/5
divide both sides by 1/5
9/20 ÷ 1/5= L
multiply by the 1/5 reciprocal/inverse
9/20 * 5/1= L
(9*5)/(20*1)= L
45/20= L
simply top & bottom by 5
9/4= L
change to mixed number
2 1/4= L
The length is 2 1/4 miles.
Hope this helps! :)