A.\(\left(\frac{4}{7}.x-1\right).3=\frac{1}{21}\)
\(\frac{4}{7}.x-1=\frac{1}{21}:3\)
\(\frac{4}{7}.x-1=\frac{1}{21}.3\)
\(\frac{4}{7}.x-1=\frac{1}{7}\)
\(\frac{4}{7}.x=1+\frac{1}{7}\)
\(\frac{4}{7}.x=\frac{8}{7}\)
\(x=\frac{8}{7}:\frac{4}{7}\)
\(x=\frac{8}{7}.\frac{7}{4}\)
\(x=2\)
Vậy x=2
C.\(\frac{2}{3}.x-\frac{1}{3}.x=\frac{5}{9}\)
\(\left(\frac{2}{3}-\frac{1}{3}\right).x=\frac{5}{9}\)
\(\frac{1}{3}.x=\frac{5}{9}\)
\(x=\frac{5}{9}:\frac{1}{3}\)
\(x=\frac{5}{9}.3\)
\(x=\frac{5}{3}\)
Vậy \(x=\frac{5}{3}\)
D. \(\left(x-2\frac{1}{4}\right).\left(\frac{-2}{3}\right).50\%=2\frac{5}{6}\)
\(x.\frac{-2}{3}-\frac{9}{4}.\frac{-2}{3}=\frac{17}{6}:\frac{1}{2}\)
\(x.\frac{-2}{3}-\frac{-3}{2}=\frac{17}{6}.2\)
\(x.\frac{-2}{3}+\frac{3}{2}=\frac{17}{3}\)
\(x.\frac{-2}{3}=\frac{17}{3}-\frac{3}{2}\)
\(x.\frac{-2}{3}=\frac{34}{6}-\frac{9}{6}\)
\(x.\frac{-2}{3}=\frac{25}{6}\)
\(x=\frac{25}{6}:\frac{-2}{3}\)
\(x=\frac{25}{6}.\frac{3}{-2}\)
\(x=\frac{25}{-4}\)
Vậy \(x=\frac{25}{-4}\)
