a) A= $\left ( \frac{-1}{5}+\frac{3}{7} \right )$:$\frac{5}{4}$+$\left ( \frac{-4}{5}+\frac{4}{7} \right )$:$\frac{5}{4}$

      = $\left ( \frac{-1}{5}+\frac{3}{7} \right )$ . $\frac{4}{5}$+$\left ( \frac{-4}{5}+\frac{4}{7} \right )$.$\frac{4}{5}$

      = $\left \lfloor \frac{-1}{5}+\frac{3}{7}+\left ( \frac{-4}{5} \right )+\frac{4}{7} \right\rfloor.\frac{4}{5}$

      = $\left \{ \left [ \left ( \frac{-1}{5} \right )+\left ( \frac{-4}{5} \right ) \right ]+\left ( \frac{3}{7}+ \frac{4}{7}\right ) \right \}.\frac{4}{5}$

      = (-1+1). $\frac{4}{5}$

      = 0. $\frac{4}{5}$

      = 0

b) B= 2022,2021 . 1954,1945 + 2022,2021 . (-1954,1945)

      = 2022,2021. [1954,1945+ (-1954,1945)]

      = 2022,2021.0

      = 0