I took over the HR department temporarily, and the way the weekly salary is calculated is differecnt from what I think it should be done. What is the proper procedure to calculate a bi-weekly salary from annual salary given?

Bi weekly salary means there is 26 checks issues during the year,
So basically the sum of the 26 chekcs have to add up to the total.
So if you basically divide the annual salary by 26 you should have what the bi weekly amount should be.

How much money will be deducted from pay check of $760 with one dependent on W4?

bi weekly salary means there is 26 checks issues during the year,
So basicly the sum of the 26 chekcs have to add up to the total.
So if you basicly divide the annual salary by 26 you should have what the bi weekly amount should be.

BINGO