Arkadasim impulse,

You can use both active voice (действительный залог) and passive voice (страдательный залог). I'd say percentagewise passive voice is less used in every day Russian in such cases. Passive voice generally is common in formal contexts or technical literature (but even here less than in English perhaps).

But if you need to use страдательный залог, here are the examples:

The sentence is written by me - Это предложение написано мной. (active voice equiv. is Я написал это предложение).

The problem is solved by me. - Задача решена мной.