Income tax in the United States
For example, if a person earns $9,276 in a year, they do not have to pay 15% of that whole amount.  The first $9,275 that they earned falls into the first tax bracket ($0  $9275, which has a 10% tax rate).  The person pays the 10% tax rate for all of their income that fell into that tax bracket.  The person has only $1 left in income that falls into the next tax bracket ($9,276  $37,650).  They only have to pay that tax bracket's tax rate of 15% on that one dollar.