smit'sschool begins at 8;15am and closes at 3;00 pm.if the short break of 10 min lunch break for 45 min,how long he actually study.

Smit's school begins at 8:15 a.m and closes at 3:00 p.m.
So, total time from 8:15 a.m to 3:00 p.m. = 6 hours and 45 minutes
Total break = 10 minutes + 45 minutes = 55 minutes
So, total time spent on studying = 6 hours 45 minutes - 55 minutes = 5 hours 50 minutes