For 2021, the amount of U.S. federal tax owed T is a function of taxable income d:

Noam has $90,000 in taxable income, and Betty has $120,000. How much more tax does Betty pay?

Noam pays 13584.5 in tax, and Betty pays 18719.5 in tax.

The difference is 18719.5 - 13584.5 = 5135.