в) $$7 \frac{1}{4} - 8 \frac{2}{9}$$;

$$7 \frac{1}{4} - 8 \frac{2}{9} = \frac{29}{4} - \frac{74}{9} = \frac{29 \cdot 9 - 74 \cdot 4}{36} = \frac{261 - 296}{36} = \frac{-35}{36} = -\frac{35}{36}$$