We know that Nick and Nora are married and have three children who are studying in college.
Also, their gross income = $47,400
Standard deduction = $12,600
Itemized deductions = $14,200
Exemption = $4,000 for each adult and each dependent
⇒ Exemption = 4,000 * 5
⇒ Exemption = $20,000
Taxable Income = Gross Income - Standard Deduction - Itemized Deduction - Exemptions
⇒ Taxable Income = 47,400 - 12,600 - 14,200 - 20,000
⇒ Taxable Income = $600
Hence, their taxable income is $600