You need to find the amount subject to withholding, subtracting from the weekly salary the amount for one withholding allowance for weekly salaries, which is 77.90$:
830 - 77.90 = 752.1 $.
Then, look in the Fed Tax tables ( http://www.opers.ok.gov/Websites/opers/images/pdfs/2016-Fed-Tax-Tables.pdf ) for a married person with a weekly payroll.
You previously found an amount of 752.1 which is greater than 521 but less than 1613$: therefore the income tax to withhold is 35.70$ + 15% of excess over $521.
Therefore, calculate the income tax due: 35.70 + (752.1 - 521) × 15 ÷ 100 = 70.37$
The total amount of income tax that will be withheld is 70.37$
