Express the decimal as an rational number through geometric series

1.213213213....

$\displaystyle \frac{ A} {1-r} \$

I understand how to do say .2222222222

as $\displaystyle \frac {2} {10}\ ( 1 + \frac { 1} {10}\ + \frac { 1} {100}\ ...)$

With my A = 2/10

and my r = 1/10

Any help would be appreciated! Im sure its me just brain farting, I cant seem to put it together.