Final answer:
Maria's tax liability cannot be calculated accurately without the 2018 tax brackets and knowledge of applicable deductions and credits. Assuming similar tax brackets to the given example, Maria's marginal tax rate would be at 10% for her total income of $9,000, but additional information is needed for a precise calculation.
Step-by-step explanation:
The subject question involves calculating Maria's tax liability which blends concepts of both earned and unearned income. Based on the information given that Maria has $2,000 of earned income from mowing lawns and $7,000 of unearned interest income, her tax liability would depend on the tax rates and laws applicable for the 2018 tax year. Assuming the example provided of a single taxpayer's income brackets and tax rates, we can determine her liability by applying her earned and unearned income to the appropriate tax brackets. However, the question does not provide the necessary tax brackets for 2018, nor does it indicate which elements such as standard deductions or personal exemptions apply to Maria. Therefore, we cannot accurately calculate her tax liability without this additional information. To understand how it works, consider the marginal tax rate example. If income up to $9,075 is taxed at 10%, and income from $9,075 to $36,900 is taxed at 15%, Maria's marginal tax rate would depend on which bracket her total income falls into. Since she has total income ($2,000 + $7,000 = $9,000), which is below $9,075, her marginal tax rate would be at 10% assuming similar tax brackets were in place in 2018.
However, calculating the exact tax liability requires a comprehensive understanding of the tax code, which could involve additional considerations such as the Kiddie Tax for unearned income of minors, standard or itemized deductions, and any relevant tax credits.