\[\left( 7\frac{5}{9} \right)^{2} - \left( 4\frac{4}{9} \right)^{2} =\]
\[= \left( 7\frac{5}{9} - 4\frac{4}{9} \right)\left( 7\frac{5}{9} + 4\frac{4}{9} \right) =\]
\[= 3\frac{1}{9} \cdot 11\frac{9}{9} = \frac{28}{9} \cdot 12 =\]
\[= \frac{28 \cdot 4}{3} = \frac{112}{3} = 37\frac{1}{3}.\]