\[Пусть\ x - задуманное\ число.\]
\[\left( x - 3\frac{5}{6} \right) + 2\frac{3}{5} = 5\frac{2}{3}\]
\[x - 3\frac{5}{6} = 5\frac{2}{3} - 2\frac{3}{5}\]
\[x = 3\frac{5^{\backslash 5}}{6} + 5\frac{2^{\backslash 10}}{3} - 2\frac{3^{\backslash 6}}{5}\]
\[x = 3\frac{25}{30} + 5\frac{20}{30} - 2\frac{18}{30}\]
\[x = 6 + \frac{27}{30} = 6\frac{27}{30}\]
\[x = 6\frac{9}{10}.\]