Here is the step by step explaination
Tax = 0.35 * Earnings (Earnings < $100,000)
Tax = 0.35 * $100,000 + 0.45 * (Earnings - $100,000) ($100,000 < Earnings < $500,000)
Tax = 0.35 * $100,000 + 0.45 * $400,000 + 0.55 * (Earnings - $500,000)
(Earnings > $500,000)