Do you know the answer?

First note that $0.999... = \frac{9}{10} +\frac{9}{100} +\frac{9}{1000} +...$

The value of the right-hand side is given by the formula:

$\frac{\frac{9}{10}}{(1-r)}$ where r = $\frac{1}{10}$ (sum of infinite series).

Calculating this formula we have $\frac{\frac{9}{10}}{(1-r)} = \frac{\frac{9}{10}}{1-\frac{1}{10}} = 1$

Or 0.9999... =x 9.99999... =10x 9=9x 1=x=0.99999...