Final answer:
Without the tax brackets for 2019, we cannot determine Gabriel's tax liability from his taxable income of $1,300,000. Taxes in the US are calculated using a progressive tax system with marginal rates applying to respective income brackets.
Step-by-step explanation:
The question relates to the calculation of tax liability based on a progressive tax system, which is a key concept in understanding personal income taxation in the United States. Gabriel's taxable income of $1,300,000 would have placed him in the highest tax bracket for the year 2019. However, without the specific tax brackets and rates for that year, we cannot accurately calculate his tax liability from the provided information. The marginal tax rate system means that each portion of income is taxed at the corresponding rate in its bracket, not that all income is taxed at the rate of the highest bracket reached. It's important to note that actual tax calculations would need to take into account various deductions, exemptions, and credits, in addition to considering the specific tax rates that were in effect for that tax year.