\(\frac{7}{8}=x-\frac{1}{10}-\frac{1}{15}-\frac{1}{21}-...-\frac{1}{120}\)
\(\frac{7}{4}=2x-\left(\frac{2}{20}+\frac{2}{30}+\frac{2}{42}+...+\frac{2}{240}\right)\)
\(\frac{7}{4}=2x-2\left(\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+...+\frac{1}{15.16}\right)\)
\(\frac{7}{4}=2x-2\left(\frac{1}{4}-\frac{1}{16}\right)\)
\(\frac{7}{4}=2x-\frac{3}{8}\)
\(2x=\frac{17}{8}\)
\(x=\frac{17}{16}\)
Vậy \(x=\frac{17}{16}\)
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