Bài `2:`
`c)` $\frac{-20}{21}$ . $\frac{-4}{5}$ `=` $\frac{20.4}{21.5}$ `=` $\frac{5.4.4}{21.5}$ `=` $\frac{16}{21}$
`g)` $\frac{-4}{14}$ . `(-6`$\frac{3}{8}$`)`
`=` $\frac{-4}{17}$ . $\frac{-51}{8}$
`=` $\frac{4.51}{17.8}$
`=` $\frac{4.17.3}{17.4.2}$
`=` $\frac{3}{2}$
`n)` `1`$\frac{1}{17}$ . `(-2`$\frac{1}{8}$`)`
`=` $\frac{18}{17}$ . $\frac{-17}{8}$
`=` $\frac{-18}{8}$
`=` $\frac{-9}{4}$
`m)` `2`$\frac{2}{5}$ . $\frac{-3}{5}$
`=` $\frac{12}{5}$ . $\frac{-3}{5}$
`=` $\frac{-36}{25}$
Bài `3:`
`f)` `-3`$\frac{1}{7}$ `:` `1`$\frac{6}{49}$
`=` $\frac{-22}{7}$ `:` $\frac{54}{49}$
`=` $\frac{-22}{7}$ . $\frac{49}{54}$
`=` $\frac{-22.49}{7.54}$
`=` $\frac{-11.2.7.7}{7.2.27}$
`=` $\frac{-77}{27}$
`q)` `(2`$\frac{2}{15}$ . $\frac{9}{17}$ . $\frac{3}{32}$`)`.`(-`$\frac{3}{17}$`)`
`=` $\frac{32}{15}$ . $\frac{9}{17}$ . $\frac{3}{32}$ $\frac{-3}{17}$
`=` $\frac{32.9.3.(-3)}{15.17.32.17}$
`=` $\frac{32}{15}$ . $\frac{9}{17}$ . `0`
`=` `0`
