[tex] - 2.1 \times a \times ( - 10) \times 2 \frac{1}{3 } = \\ 21 \times 2 \frac{1}{3} \times a = \frac{21 \times 7}{3} a = 49a = \\ 49 \times ( - 1 \frac{1}{7} ) = - \frac{49 \times 8}{7} = - 56[/tex]

[tex] - 2 \frac{2}{5} x \times \frac{3}{7} y = - \frac{12 \times 3}{5 \times 7} xy = - \frac{36}{35} xy = \\ - \frac{36}{35} \times ( - 7) \times 1 \frac{1}{4} = \frac{36 \times 7 \times 5}{35 \times 4} = 9[/tex]