Check out my eHow article on how to do percentage problems:
http://www.ehow.com/how_4816051_solve-percentage-problems.html
For each, do x/100=is/of
For the first one, it's 4/100=is/$200.00 so is=$8.
For the second one, it's 4/100=is/$220.00 so is=$8.80.
For these, note that the word "of" implies multiplication, so you just as easily could have done .04*$200 and .04*$220 and obtained the same answers.