3) (−5/9 + 1 20/21) · (3/49 − 1 7/9) · (−6) =

\(-\frac{5}{9}+1\frac{20}{21}=-\frac{35}{63}+\frac{123}{63}=\frac{88}{63}\).

\(\frac{3}{49}-1\frac{7}{9}=\frac{27}{441}-\frac{784}{441}=-\frac{757}{441}\).

Тогда \(\frac{88}{63}\cdot(-\frac{757}{441})\cdot(-6)=\frac{133232}{9261}\).

Ответ: \(\frac{133232}{9261}\).