Làm hộ mik câu 16;17;18

Đáp án:

 $16)\dfrac{-21}{85}\\
17)
0\\
18)
\dfrac{-108}{7}$

Giải thích các bước giải:

 $16)\left ( 2\dfrac{2}{15}.\dfrac{9}{17}.\dfrac{3}{32} \right ):\left ( -\dfrac{3}{7} \right )\\
=\dfrac{32}{15}.\dfrac{9}{17}.\dfrac{3}{32}.\dfrac{-7}{3}\\
=\dfrac{32}{15}.\dfrac{9}{17}.\dfrac{-7}{32}\\
=\dfrac{32.9.(-7)}{15.17.32}\\
=\dfrac{3^2.(-7)}{3.5.17}\\
=\dfrac{-21}{85}\\
17)
\left ( \dfrac{-3}{4}+\dfrac{2}{5} \right ):\dfrac{3}{7}+\left ( \dfrac{3}{5}+\dfrac{-1}{4} \right ):\dfrac{3}{7}\\
=\left ( \dfrac{-3}{4}+\dfrac{2}{5} \right ).\dfrac{7}{3}+\left ( \dfrac{3}{5}+\dfrac{-1}{4} \right ).\dfrac{7}{3}\\
=\dfrac{3}{7}.\left ( \dfrac{-3}{4}+\dfrac{2}{5}+\dfrac{3}{5}-\dfrac{1}{4} \right )\\
=\dfrac{3}{7}.\left ( \dfrac{-4}{4}+\dfrac{5}{5} \right )\\
=\dfrac{3}{7}.(-1+1)\\
=0\\
18)
\dfrac{7}{8}:\left ( \dfrac{2}{9}-\dfrac{1}{18}\right ):\dfrac{7}{8} :\left ( \dfrac{1}{36}-\dfrac{5}{12} \right )\\
=\dfrac{7}{8}:\left ( \dfrac{4}{18}-\dfrac{1}{18}\right ):\dfrac{7}{8} :\left ( \dfrac{1}{36}-\dfrac{15}{36} \right )\\
=\dfrac{7}{8}:\dfrac{3}{18}:\dfrac{7}{8}:\dfrac{-14}{36}\\
=\dfrac{7}{8}:\dfrac{1}{6}:\dfrac{7}{8}:\dfrac{-7}{18}\\
=\dfrac{7}{8}.6.\dfrac{8}{7}.\dfrac{-18}{7}\\
=\dfrac{7.6.8.(-18)}{8.7.7}\\
=\dfrac{6.(-18)}{7}\\
=\dfrac{-108}{7}$