Give your answer in the 24-hour clock form, for example, 15:00.

Alex worked with his teacher on an experiment before going dinner that lasted 35 minutes. He finished his dinner at 19:45. If the experiment lasted 2 h and 20 min, at what time did he start the experiment?

Total elapsed time: 35 min + 2 h 20 min = 2 h 55 min

End time: 19:45

Start time: 19:45-2 h 55 min = 16:50

So the answer is 16:50.