Consider Mark and Jens income and deductions. They file a joint return. Their combined gross income is $168,000. They have the following possible amounts which qualify as itemized deductions to consider: $4,100 in real estate taxes, $4,125 in interest paid on their home mortgage, and $1,200 interest paid on a home-equity loan. They have three children who are claimed as dependents. What is the Johnsons taxable income? Label each value used in the calculation carefully.

Please explain where does exemption come from