How to calculate hours in excel

I need an equation that will automatically add and subtract and give me total hours. this is the format. When I input start time and end time and brake time it should automatically calculate hours – brakes giving me total hours worked. What equations do I use I havent used excel since High school Cell B1 Cell B2 Cell B3 Cell B4
Start TimeEnd Time Brakes Total Hours
12.00 am 6.00 pm 4.30 pm- 5.00 pm 5.50
Answer #1

Answer #2
I see thanx mate
look what I get?