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
funny i typed моя проблема and they marked it wrong and gave my exact answer as the correct answer. haha
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
what is the difference with -моё депа
Моё дела is neuter while Моя проблема is feminine