Решите уравнение: 1/3*x+1/5*x+1/6*x=21/40.

\[\frac{1^{\backslash 10}}{3}x + \frac{1^{\backslash 6}}{5}x + \frac{1^{\backslash 5}}{6}x = \frac{21}{40}\]

\[\frac{10 + 6 + 5}{30}x = \frac{21}{40}\]

\[\frac{21}{30}x = \frac{21}{40}\]

\[x = \frac{21 \cdot 30}{40 \cdot 21}\]

\[x = \frac{3}{4}.\]