Sometimes taxpayers must estimate tax owed using a simplified, fictional rate to practice. Suppose a taxpayer has taxable income of $75,000 after deductions and a flat example tax rate of 12% (this is a fictional simplification for practice). Multiply taxable income by the rate to estimate tax liability; then compare to withheld amounts to see if adjustments are needed. This exercise is purely illustrative — do not use it as legal guidance. It helps you practice percentage math needed for estimated payments or withholding changes.