Why not: мой проблем?
Because the Russian word for "problem" is "проблема" and it is feminine. "Моя" is the possessive pronoun used with feminine nouns
Could I use also "задача"?
Задача is more like a homework or some task you need to do. Prolly your dictionary or translator mentioned it as a synonym because it connected "math problem" with a homework :-)
Thanks! My textbook tells me the same but it was the only word I had, so I was using it all the time :P
funny i typed моя проблема and they marked it wrong and gave my exact answer as the correct answer. haha
It is no surprise that the word "problem" is feminine.
It is not me being sexist, it is the language. :-)
And yet, the word "невежливый" is masculine. Huh. :-)