"How is your mother?"
Translation:तुम्हारी माँ कैसी हैं?
तुम्हारी is less personal/more formal than तेरी but more personal/less formal than आपकी.
In general, you can use the तुम forms (like तुम्हारी) with most people who are around the same age as you or younger (except in a formal/professional context where आप forms would be more appropriate). It might also be a good idea to start off with आप forms for strangers and then move on to तुम once you get to know the person a little.