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\(a)\)\(x\div3\frac{1}{4}=\frac{-1}{13}\)
\(x\div\frac{13}{4}=\frac{-1}{13}\)
\(x=\frac{-1}{13}\times\frac{13}{4}\)
\(x=\frac{-1}{4}\)
\(b)\)\(x-\frac{13}{20}=\frac{11}{4}+\frac{-7}{5}\)
\(x-\frac{13}{20}=\frac{27}{20}\)
\(x=\frac{27}{20}+\frac{13}{20}\)
\(x=\frac{40}{20}\)
\(x=\frac{4}{2}=2\)
\(c)\)\(\left(1\frac{1}{3}-\frac{3}{4}x\right).120\%=\frac{4}{5}\)
\(\left(1\frac{1}{3}-\frac{3}{4}x\right).\frac{6}{5}=\frac{4}{5}\)
\(\left(\frac{4}{3}-\frac{3}{4}x\right).\frac{6}{5}=\frac{4}{5}\)
\(\left(\frac{4}{3}-\frac{3}{4}x\right)=\frac{4}{5}\div\frac{6}{5}\)
\(\left(\frac{4}{3}-\frac{3}{4}x\right)=\frac{4}{5}\times\frac{5}{6}\)
\(\left(\frac{4}{3}-\frac{3}{4}x\right)=\frac{2}{3}\)
\(\frac{4}{3}-\frac{3}{4}x=\frac{2}{3}\)
\(\frac{3}{4}x=\frac{4}{3}-\frac{2}{3}\)
\(\frac{3}{4}.x=\frac{2}{3}\)
\(x=\frac{2}{3}\div\frac{3}{4}\)
\(x=\frac{2}{3}\times\frac{4}{3}\)
\(x=\frac{8}{9}\)