If the ending time was 10:35 and 45 minutes passed:
35 - 45 = -10 that does not work. Sooo, what we are going to do is take away 36.
So instead of 10:35, we have 9:59, and instead of 45, we have 9.
59 - 9 = 50
So our answer is: 9:50 was the start time