Помогите решить пример 5 класс

$\frac{(7-6 \frac{7}{20}):6 \frac{1}{2}+9 \frac{9}{10}}{(1 \frac{1}{5}:36+1 \frac{1}{5}: \frac{1}{4}-1 \frac{5}{16}): \frac{169}{24}}=20\\ \\ 1) 7-6 \frac{7}{20}= \frac{13}{20} \\ \\ 2) \frac{13}{20}:6 \frac{1}{2}= \frac{13}{20}* \frac{2}{13}= \frac{1}{10} \\ \\ 3) \frac{1}{10}+9 \frac{9}{10}=10$
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$4) 1\frac{1}{5}:36= \frac{6}{5}* \frac{1}{36}= \frac{1}{30} \\ \\ 5) 1\frac{1}{5}: \frac{1}{4}= \frac{6}{5}* \frac{4}{1}= \frac{24}{5} \\ \\ 6) \frac{1}{30}+\frac{24}{5}= \frac{1+144}{30}= \frac{145}{30}= \frac{29}{6} \\ \\ 7) \frac{29}{6}-1 \frac{5}{16}=\frac{29}{6}- \frac{21}{16}= \frac{232-63}{48} = \frac{169}{48} \\ \\ 8)\frac{169}{48}: \frac{169}{24}=\frac{169}{48}* \frac{24}{169}= \frac{24}{48}= \frac{1}{2}=0,5$
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$9) \frac{10}{0,5}= 20$