Suppose that you work at the Peacock Blue store for 40 hours over five days at a rate of $8.75/hour. You then quit your job. Deductions are FICA (7.65%), federal withholding (12%), and state withholding (8%). Your expenses are transportation at $4.25/day, lunch at $3.85/day, and black slacks required for work at $29.95. How much is your discretionary income for the week?

The discretionary income will be $182.78.

40hrs * $8.75 = $350 earned before taxes

Then, add up all the percentages for the deductions. 
7.65% + 12% + 8% = 27.65% (turn into decimal -> .2765)

Multply work pay by the percent.

$350*.2765 = $96.775 (taxes withheld)

Now, add up all your expenses for those 5 days:
transportation: $4.25 a day = $21.25
lunch: $3.85 a day = $19.25
black slacks: $29.95

total expenses: $70.45

Discretionary Income = $350 - $96.775(taxes) - $70.45(expenses) = $182.78