My tone talking to my mother

One day i was on my phone and my mom asked me to do something for her...I think it was like watch her daycare kids while she went to the store, to pick up my brother from work and take my two sisters to work. I said okay but I think she thought i was trying to get smart. I wasn't i just said okay. But that turned to something else and she was screaming. Saying that she does everything for everyone and she asks us to do simple things and we get attitudes but i wasn't upset or i didn't have an attitude i just say okay. Then i felt she was mad at me the rest of the day. But later that night i had to talk to her. I told her that i didn't try to get smart...maybe it was just the way that i said it. She understood and she expressed her feelings of how she doesn't feel appreciated by anyone and i told her that i really appreciate her. That showed tone because the tone of my voice made her think that i was being smart when i really wasn't.