Timesheets

I have been using Excel for quite a while but still do not know much about it.
I am busy trying to make our employee timesheets/payslips more user friendly.
Some employees in our company are paid according to the exact time they have worked e.g from 07:30 to 16:15 minus 30 minutes lunch. How would I set up a formula for this i.e.:

Time ended - time started - 30 minutes lunch = hours:minutes worked

How do I do this without having to put in a formula for each line so that
I wouldn't have to write =B1-A1-C1 and the next line =B2-A2-C2
i.e. How do I put in one formula that would cover entries for 30 rows?

Assuming this formula is entered in D1.
Select D1 and move your mouse to the bottom right corner of D1. You should see a "+" sign. Select the bottom right corner of D1 and drag it down to D2,D3, D4.... Dn - till the number of rows for which you need the formula?
Is this okay ?

The answers were exactly what I wanted to know.
Thank you.

Or double-click the handle. It will auto-fill formulas as long as the adjacent cell is not empty