3/7x+5/21x+1/3x=
2/7​

Ответ:

[tex] \frac{3}{7} x + \frac{5}{21} x + \frac{1}{3} x = \frac{2}{7} \\ 9x + 5x + 7x = 6 \\ 21x = 6 \\ x = \frac{6}{21} \\ x = \frac{2}{7} \\ check : \\ \frac{3}{7} \times \frac{2}{7} + \frac{5}{21} \times \frac{2}{7} + \frac{1}{3} \times \frac{2}{7} = \frac{2}{7} \\ \frac{2}{7} = \frac{2}{7} \\ answer : x = \frac{2}{7} [/tex]