6)
\(=\dfrac{3}{11}+\dfrac{8}{11}+-\dfrac{5}{7}\)
\(=\left(\dfrac{3}{11}+\dfrac{8}{11}\right)+-\dfrac{5}{7}\)
\(=1+\dfrac{-5}{7}\)
\(=\dfrac{7}{7}+-\dfrac{5}{7}\)
\(=\dfrac{2}{7}\)
7)
\(=\dfrac{10}{20}+\dfrac{15}{20}-\left(\dfrac{15}{20}-\dfrac{16}{20}\right)\)
\(=\dfrac{25}{20}-\left(-\dfrac{1}{20}\right)\)
\(=\dfrac{13}{10}\)
8)
\(=\left(\dfrac{9}{24}+-\dfrac{18}{24}+\dfrac{14}{24}\right):\dfrac{5}{6}+\dfrac{1}{2}\)
\(=\dfrac{5}{24}:\dfrac{5}{6}+\dfrac{1}{2}\)
\(=\dfrac{5}{24}.\dfrac{6}{5}+\dfrac{1}{2}\)
\(=\dfrac{1}{4}+\dfrac{1}{2}\)
\(=\dfrac{1}{4}+\dfrac{2}{4}\)
\(=\dfrac{3}{4}\)
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