Agrant writer had a taxable income of $37,450 last year. if he paid 10% of his income between $0 and $8350, 15% of his income between $8350 and $33,950, and 25% of his income between $33,950 and $37,450 in federal income tax, how much did the grant writer pay in federal income tax last year?

  10% of 8350=$835. 

15% of 25600(8350 from 33950) =25,600 15% of 25600= 3840. 
25% of 3500. (32450 minus 33950= 3500 25% of 3500 =875. 

Add the three and you get $5550. Of course you could have eliminated step two and three by anticipating a tax that far exceeded the other choices which were way to low to even consider. 
Work this out for yourself. It is simple and fun when you get the hang of it.

Hope This Helped! :3