Help me plz it’s important

Me! 50 points! why does when we come home, our door is unlocked and there is grease on the door knob, me solve this , and i don't know what category this goes under

If a baby uses 15 diapers in 2 days how many diapers will the baby use in a year

Hi i’m not sure how to do question 20 if u could explain how to do it that’d b great