Question

⅓x+⅕x+⅙x=двадцять одна сорокова ​

Answer 1

$\displaystyle\bf\\\frac{1}{3} x+\frac{1}{5} x+\frac{1}{6} x=\frac{21}{40} \\\\\\\Big(\frac{1}{3} +\frac{1}{5} +\frac{1}{6} \Big)\cdot x=\frac{21}{40}\\\\\\\frac{10+6+5}{30} \cdot x=\frac{21}{40} \\\\\\\frac{21}{30} x=\frac{21}{40} \\\\\\x=\frac{21}{40} :\frac{21}{30} =\frac{21}{40} \cdot\frac{30}{21} =\frac{3}{4} =0,75\\\\\\Otvet \ : \ x=0,75$