[tex]x - nr.[/tex]
[tex] \frac{1}{3} \times x + \frac{x}{4} = 0.(21)[/tex]
[tex] \frac{x}{3} + \frac{x}{4} = \frac{21}{99} [/tex]
[tex] \frac{x}{3} + \frac{x}{4} = \frac{7}{33} [/tex]
[tex] \frac{4x}{12} + \frac{3x}{12} = \frac{7}{33} [/tex]
[tex] \frac{4x + 3x}{12} = \frac{7}{33} [/tex]
[tex] \frac{7x}{12} = \frac{7}{33} [/tex]
[tex]33 \times 7x = 12 \times 7 \: | \div 7[/tex]
[tex]33x = 12[/tex]
[tex]x = \frac{12}{33} [/tex]
[tex]x = 0.(36)[/tex]
