Oh my goodness I am so sorry! I told you the wrong thing yesterday. a2 should be the amount that her earned income is over 25750. So let me walk you through this again correctly. First you look at the earned income, and then look at the chart on the left to find the range that it falls between. So in this case 43000 is between the 25750 and 62450. Which means that the base tax amount of 3862.50 (following the table over). What this means is that anyone making between 25750 and 62450 has to pay 3862.50 in taxes no matter what. But it wouldn't be fair for someone who makes 60,000 to pay the same amount as someone who makes 30,000 even though those are in the same range. So that is where the % and the last 2 columns of the chart come in. If someone makes over 25,750 they have to pay 28% taxes on all their earnings over the 25750 amount. So in this case, since Mary earned over 25,750 she has to pay 28% on the amount over that she earned. 43,000-25,750=17,250. She still owes 28% tax on $17,250. Find 28% = 0.28*17250=4830. She has to pay an additional 4830 in taxes. So her total tax amount is 4830+3862.50=8692.50.