X=length y=width Area (rectangle)=length x width we suggest this system of equations: y=x/5 xy=9/20 solve this system of equations by substitution method: x(x/5)=9/20 x²/5=9/20 Least common multiple=20 4x²=9 x²=9/4 x=⁺₋√(9/4) we have two solutions: x₁=-3/2 it does not validate x₂=3/2 ⇒y=x/5=(3/2)/5=3/10
The dimensions of the lake are: lengh=3/2 miles width=3/10 miles
to check: Area=3/2 miles x 3/10 miles=9/20 miles². width is 1/5 the length of the lake ⇒ 3/10 miles=(3/2) /5 miles
