Answer
a) $(N^{(-3)}H_{4}^{(+1)})_{2}Cr_{2}^{(+6)}O_{7}^{(-2)} \rightarrow N_{2}^{(0)} + Cr_{2}^{(+3)}O_{3}^{(-2)} + 4H_{2}^{(+1)}O^{(-2)}$
b) $2Na^{(+1)}N^{(+5)}O_{3}^{(-2)} \rightarrow 2Na^{(+1)}N^{(+3)}O_{2}^{(-2)} + O_{2}^{(0)}$
Work Step by Step
a) $(N^{(-3)}H_{4}^{(+1)})_{2}Cr_{2}^{(+6)}O_{7}^{(-2)} \rightarrow N_{2}^{(0)} + Cr_{2}^{(+3)}O_{3}^{(-2)} + 4H_{2}^{(+1)}O^{(-2)}$
b) $2Na^{(+1)}N^{(+5)}O_{3}^{(-2)} \rightarrow 2Na^{(+1)}N^{(+3)}O_{2}^{(-2)} + O_{2}^{(0)}$