You don't need the acre conversions for this. You know that three feet = one yard, expressed as [tex]3f=y[/tex]. If you square this (one square foot is literally one foot squared, the same goes for yards), then [tex](3f)^{2} = y^{2} [/tex], which means [tex]9 (f^{2})= y^{2} [/tex], so there are nine square feet in a square yard.
