a) $\frac{2}{7}$ . $\frac{-5}{11}$ + $\frac{2}{7}$ . $\frac{-4}{11}$ + $\frac{2}{7}$ . $\frac{-2}{11}$
= $\frac{2}{7}$ . ($\frac{-5}{11}$ + $\frac{-4}{11}$ + $\frac{-2}{11}$)
= $\frac{2}{7}$ . -1
= $\frac{-2}{7}$
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b) $\frac{-3}{8}$ . $\frac{2}{15}$ + $\frac{-3}{8}$ . $\frac{13}{15}$ + 1 . $\frac{3}{8}$
= $\frac{-3}{8}$ . ($\frac{2}{15}$ + $\frac{-3}{15}$ + 1)
= $\frac{-3}{8}$ . 2
= $\frac{-3}{4}$