Giúp mình làm bt 2 này với ạ

Đáp án:

 $a) \dfrac{4}{3}\\
b)\dfrac{9}{4}\\
c)\dfrac{5}{4}\\
d)
\dfrac{11}{7}\\
e) \dfrac{-6}{5}\\
f) \dfrac{-2}{3}\\
g) \dfrac{2}{7}\\
h) \dfrac{5}{9}\\
i) \dfrac{4}{3}\\
k) \dfrac{13}{12}\\
l)\dfrac{5}{12}\\
m) -118$

Giải thích các bước giải:

 $a) 6\dfrac{4}{5}-\left ( 1\dfrac{2}{3}+3\dfrac{4}{5} \right )=6\dfrac{4}{5}-  1\dfrac{2}{3}-3\dfrac{4}{5}\\
=(6-1-3)+\left ( \dfrac{4}{5}-\dfrac{2}{3}-\dfrac{4}{5} \right )\\
=2+\dfrac{-2}{3}=\dfrac{2.3}{3}-\dfrac{2}{3}=\dfrac{4}{3}\\
b)6\dfrac{5}{7}-\left ( 1\dfrac{3}{4}+2\dfrac{5}{7} \right )=6\dfrac{5}{7}- 1\dfrac{3}{4}-2\dfrac{5}{7} \\
=(6-1-2)+\left ( \dfrac{5}{7}-\dfrac{3}{4}-\dfrac{5}{7} \right )\\
=3-\dfrac{3}{4}=\dfrac{3.4}{4}-\dfrac{3}{4}=\dfrac{9}{4}\\
c)7\dfrac{5}{9}-\left ( 2\dfrac{3}{4}+3\dfrac{5}{9} \right )=7\dfrac{5}{9}- 2\dfrac{3}{4}-3\dfrac{5}{9} \\
=(7-2-3)+\left ( \dfrac{5}{9}-\dfrac{3}{4}-\dfrac{5}{9} \right )\\
=2-\dfrac{3}{4}=\dfrac{8}{4}-\dfrac{3}{4}=\dfrac{5}{4}\\
d)
7\dfrac{5}{11}-\left ( 2\dfrac{3}{7}+3\dfrac{5}{11} \right )=7\dfrac{5}{11}-2\dfrac{3}{7}-3\dfrac{5}{11} \\
=(7-2-3)+\left ( \dfrac{5}{11}-\dfrac{3}{7}-\dfrac{5}{11} \right )\\
=2-\dfrac{3}{7}=\dfrac{14}{7}-\dfrac{3}{7}=\dfrac{11}{7}\\
e) \dfrac{-3}{5}.\dfrac{5}{7}+\dfrac{-3}{5}.\dfrac{3}{7}+\dfrac{-3}5.\dfrac{6}{7}\\
=\dfrac{-3}{5}.\left ( \dfrac{5}{7}+\dfrac{3}{7}+\dfrac{6}{7} \right )\\
=\dfrac{-3}{5}.\dfrac{14}{7}=\dfrac{-3}{5}.2=\dfrac{-6}{5}\\
f) \dfrac{1}{3}.\dfrac{4}{5}+\dfrac{1}{3}.\dfrac{6}{5}-\dfrac{4}{3}\\
=\dfrac{1}{3}.\left ( \dfrac{4}{5}+\dfrac{6}{5}-4 \right )\\
=\dfrac{1}{3}.(2-4)=\dfrac{-2}{3}\\
g) \dfrac{4}{19}.\dfrac{-3}{7}+\dfrac{-3}{7}.\dfrac{15}{19}+\dfrac{5}{7}\\
=\dfrac{-3}{7}.\left ( \dfrac{4}{19}+\dfrac{15}{19} \right )+\dfrac{5}{7}\\
=\dfrac{-3}{7}.1+\dfrac{5}{7}=\dfrac{2}{7}\\
h) \dfrac{5}{9}.\dfrac{7}{13}+\dfrac{5}{9}.\dfrac{9}{13}-\dfrac{5}{9}.\dfrac{3}{13}\\
=\dfrac{5}{9}.\left ( \dfrac{7}{13}+\dfrac{9}{13}-\dfrac{3}{13} \right )\\
=\dfrac{5}{9}.\dfrac{13}{13}=\dfrac{5}{9}\\
i) (-2)^2-1\dfrac{5}{27}.\left ( \dfrac{3}{2} \right )^2\\
=4-\dfrac{32}{27}.\dfrac{9}{4}\\
=4-\dfrac{8}{3}=\dfrac{12}{3}-\dfrac{8}{3}=\dfrac{4}{3}\\
k) \dfrac{75}{100}-\left ( 1,25-2\dfrac{3}{4} \right ):\dfrac{\left | -3^2 \right |}{2}\\
=\dfrac{3}{4}-\left ( \dfrac{5}{4}-\dfrac{11}{4} \right ):\dfrac{9}{2}\\
=\dfrac{3}{4}-\dfrac{-6}{4}.\dfrac{2}{9}\\
=\dfrac{3}{4}+\dfrac{1}{3}=\dfrac{9}{12}+\dfrac{4}{12}=\dfrac{13}{12}\\
l) \dfrac{3}{4}-\dfrac{1}{4}.\left ( \dfrac{3}{2}-\dfrac{1}{6} \right )\\
=\dfrac{3}{4}-\dfrac{1}{4}.\left ( \dfrac{9}{6}-\dfrac{1}{6} \right )\\
=\dfrac{3}{4}-\dfrac{1}{4}.\dfrac{8}{6}\\
=\dfrac{3}{4}-\dfrac{1}{3}=\dfrac{9}{12}-\dfrac{4}{12}=\dfrac{5}{12}\\
m) \left | 0,8-2\dfrac{4}{5} \right |-(-3).(-4).5:\dfrac{50}{100}\\
=\left | \dfrac{8}{10}-\dfrac{14}{5} \right |-12.5:\dfrac{1}{2}\\
=\left | \dfrac{8}{10}-\dfrac{14.2}{10} \right |-60.2\\
=\dfrac{20}{10}-30=2-120=-118$