I'm having so much trouble with tax calculation questions.

Yvonne Jerc has an adjusted gross income of $75,000, a taxable income of $65,450 and itemized deductions and exemptions totaling $9,550. What is Ms. Jerc's average effective tax rate?

15.0%

18.3%

20.7%

28.0%

It is based off of:

If taxable income is The tax is

Not over $36,900 15% of taxable income

Over $36,900 and less than $89,150 $5,535 plus 28% of the excess over $36,900

Over $89,150 and less than $140,000 $20,165 plus 31% of the excess over $89,150

I calculated 28% of 28,550 which is $7,994. I then added $7,994 + $5,535 = $13,529

13,529/75000 = 18.03?

Are deductions suppose to be included in the calculation? I'm just not grasping what the actual formula is and how to calculate it.