How would you make a program that calculates personal income tax?

I need to make a program for a school assignment. It has to be a program that calculates the income tax of an individual. So as an example, if a person gets paid 5000 dollars a year and they made 6000 dollars in side hustle or freelance work, that makes their income 11,000 dollars. Which puts them in a tax rate of 22% so we would multiply 11,000 * 0.22 and that’s the amount of tax they owe. Ideally, this should be able to tax every single cent that someone makes from any source. But given how complex that is, I’m only going to make it work for yearly income from a job and any other sources of income.