Mr. John Doe was figuring out his federal income tax his income was $26,800, but he was able to subtract $5500 in deduction he pays 15% of the remaining income and tax how much did he pay

His taxable income: 26,800 - 5,500 = 21,300

15% of his taxable income: 21,300 * 0.15 = 3,195

It's difficult to understand what you are asking for, so here is what I think you're asking for. Correct me if I'm wrong.