If we remember what an analog clock looks like (the circle with twelve marks for the hours of the day), then let's imagine the small hour hand first starting on the big 10. Since it asks 14 hours
before her appointment, we need to move that hour hand 14 hours back, or counter-clockwise, which is the opposite direction a clock normally moves. Start from 10AM and move the hour hand backwards. When it moves one hour back, it lands on 9AM, which leaves 13 more hours to go. We turn it again to 8AM, then 7 AM, then 6 AM, then 5 AM. That's a total of 5 hours we've moved back. Let's keep going, 4AM, 3AM, 2 AM, 1AM, and 12PM midnight. Since we've turned back to midnight, we've now gone from Tuesday to Monday. We've moved back a total of 10 hours now, so only 4 more hours left to turn back the clock to answer the question. From 12PM midnight, the next hour backwards is 11PM, then 10PM, then 9PM, then 8PM. That's the last four hours that we needed to turn back the clock. So, if the doctor told Yvonne that she cannot eat fourteen hours before her appointment, and we turn the clock back fourteen hours from 10AM on Tuesday, then we know 8PM on Monday is the last time she can eat before her appointment.