To determine how much sales tax will be, we need to begin with our price:
$13.22
$13.22 is 100% of the price, before tax. Tax is based on this percentage, so we need to find out what one percent of $13.22 is.
13.22 / 100 = .1322
.1322 is one percent of $13.22. Since we are looking for four percent of 13.22, we multiply our 1% (.1322) by 4.
.1322 x 4 = .5288
$0.5288 is 4% of $13.22. So, we add that to $13.22 to find our answer, after tax.
$0.5288 + $13.22 = $13.7488, or $13.75 if you round up.