Answer:
[tex]x=\dfrac{131}{333}[/tex]
Step-by-step explanation:
Assign the decimal to a variable:
Let [tex]x=0.\overline{393}[/tex]
Multiply both sides by 1000:
[tex]\implies x \cdot 1000=0.\overline{393} \cdot 1000[/tex]
[tex]\implies 1000x=393.\overline{393}[/tex]
Subtract the first equation from the second to eliminate the part after the decimal:
[tex]\begin{array}{r r c r}& 1000x & = & 393.\overline{393} \\\\- & x & = & 0.\overline{393} \\\\\cline{2-4} \\& 999x & = & 393 \\\end{array}[/tex]
Divide both sides by 999:
[tex]\implies \dfrac{999x}{999}=\dfrac{393}{999}[/tex]
[tex]\implies x=\dfrac{393}{999}[/tex]
Reduce the fraction:
[tex]\implies x=\dfrac{393 \div 3}{999 \div 3}[/tex]
[tex]\implies x=\dfrac{131}{333}[/tex]