Bài 9 

$\dfrac{7}{17}$ + $\dfrac{6}{5}$ = $\dfrac{35}{85}$ + $\dfrac{102}{85}$ = $\dfrac{137}{85}$

$\dfrac{12}{9}$ - $\dfrac{7}{13}$ = $\dfrac{156}{117}$ + $\dfrac{63}{117}$ = $\dfrac{219}{117}$

$\dfrac{5}{6}$ × $\dfrac{4}{7}$ = $\dfrac{20}{42}$ = $\dfrac{10}{21}$

$\dfrac{3}{4}$ ÷ $\dfrac{5}{8}$ = $\dfrac{3}{4}$ × $\dfrac{8}{5}$ = $\dfrac{24}{20}$ = $\dfrac{6}{5}$

Bài 10 

$\dfrac{8}{5}$ - $\dfrac{18}{27}$ = $\dfrac{8}{5}$ - $\dfrac{2}{3}$ = $\dfrac{24}{15}$ - $\dfrac{10}{15}$ = $\dfrac{14}{15}$

$\dfrac{12}{20}$ - $\dfrac{6}{18}$ = $\dfrac{3}{5}$ - $\dfrac{1}{3}$ = $\dfrac{9}{15}$ - $\dfrac{5}{15}$ = $\dfrac{4}{15}$

$\dfrac{8}{24}$ - $\dfrac{5}{25}$ = $\dfrac{1}{3}$ - $\dfrac{1}{5}$ = $\dfrac{5}{15}$ - $\dfrac{3}{15}$ = $\dfrac{2}{15}$

$\dfrac{18}{21}$ - $\dfrac{12}{27}$ = $\dfrac{6}{7}$ - $\dfrac{4}{9}$ = $\dfrac{54}{63}$ - $\dfrac{28}{63}$ = $\dfrac{26}{63}$

$\dfrac{8}{12}$ - $\dfrac{20}{50}$ = $\dfrac{2}{3}$ - $\dfrac{2}{5}$ = $\dfrac{10}{15}$ - $\dfrac{6}{15}$ = $\dfrac{4}{15}$

$\dfrac{10}{12}$ - $\dfrac{12}{36}$ = $\dfrac{5}{6}$ - $\dfrac{1}{3}$ = $\dfrac{5}{6}$ - $\dfrac{2}{6}$ = $\dfrac{3}{6}$ = $\dfrac{1}{2}$

$\text{Xin câu trả lời hay nhất cho nhóm ạ !}$

Đáp án:

Giải thích các bước giải:

$\dfrac{7}{17}$ + $\dfrac{6}{5}$ = $\dfrac{35}{105}$ + $\dfrac{104}{105}$ = $\dfrac{139}{105}$

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$\dfrac{12}{9}$ - $\dfrac{7}{13}$ = $\dfrac{156}{117}$ - $\dfrac{63}{117}$ = $\dfrac{93}{117}$

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$\dfrac{5}{6}$ x $\dfrac{4}{7}$ = $\dfrac{5×4}{6×7}$ = $\dfrac{20}{42}$

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$\dfrac{3}{4}$ : $\dfrac{5}{8}$ = $\dfrac{3}{4}$ x $\dfrac{8}{5}$ = $\dfrac{3×8}{4×5}$ = $\dfrac{3}{20}$

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Mình sr, chỉ làm đc vậy thui ak