What is -0.333333333333333 as a fraction?

Assuming the decimals go to inifinity.; it should be written as

-0.3333.... ( Note the periods. This inidicates to mathemticians that it recurs to infinity).

-0.333.... = -1/3

Method

Let P = -0.3333....

10P = -3.33333...

Subtract

9P = -3 Note the recurring decimals subtract to zero.

P = -3/9

P = -1/3