a)10$\frac{2}{7}$ - ( 3$\frac{4}{9}$ + 4$\frac{2}{7}$ )
= 10$\frac{2}{7}$ - 3$\frac{4}{9}$ + 4$\frac{2}{7}$
= (10$\frac{2}{7}$ + 4$\frac{2}{7}$) - 3$\frac{4}{9}$
= 14$\frac{2}{7}$ - 3$\frac{4}{9}$
= $\frac{100}{7}$ - $\frac{31}{9}$
=$\frac{683}{63}$
b)(10$\frac{2}{9}$ - 2$\frac{3}{5}$) - 6$\frac{2}{9}$
= 10$\frac{2}{9}$ - 2$\frac{3}{5}$ - 6$\frac{2}{9}$
= (10$\frac{2}{9}$ - 6$\frac{2}{9}$) - 2$\frac{3}{5}$
= 4$\frac{2}{9}$ - 2$\frac{3}{5}$
= $\frac{38}{9}$ - $\frac{13}{5}$
= $\frac{73}{45}$