3000 ft square = 50 ozes of grass seed
7200 ft square = ?
cross multiply
[tex]\begin{gathered} \text{amount n}eeded=\frac{7200\times50}{3000} \\ \text{amount n}eeded=\frac{360000}{3000} \\ \text{amount n}eeded=\text{ 120 oz of grass s}eed \end{gathered}[/tex]