Holly has $10.00. She saw a purse in a catalog that was marked $14.95 plus 5% sales tax. How much more does Holly need to buy the purse?

For this case we will first look for the total cost of the purse.
 We then have the following rule of three:
 14.95 $ > 100%
 x > 105%
 Clearing x we have:
 x = (105/100) * (14.95)
 x = 15.6975 $
 The amount needed to buy the purse is:
 15.6975 - 10 = 5.6975 $
 
 holley needs 5.6975 $ to buy the purse