Just as a side note (as you do not need it for this question), an hour = 60 minutes, not 100 minutes.
Math lessons start at 9:00 A.M., and lasts for 55 minutes. Add 0:55 to 9:00
9:00 + 0:55 = 9:55
9:55 A.M. is when math lessons end.
hope this helps
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