If the school day starts at 8:50am and ends at 3:15pm. There is a playtime break at 10:40am until 10:55am and a lunch break from 12 noon until 1:05pm. How long is a school day

Lets add together breaks and all day long:

all day: from 8:50 to 15:15: that is 6 hours and 25 minutes, that is in minutes:

all day = 6*60 + 25 = 385 minutes

breaks:

play: 10:40 to 10:55: that is 15 minutes

lunch: 12:00 to 1:05: that is one hour and 5 minutes, or 65 minutes

breaks = 15 + 65 = 80 minutes

So the school day of work is: 385 - 80 = 305 minutes

That is 5 hours and 5 minutes

Remember, an hour is 60 mins.