Liz wants to buy her favorite musical group's new CD. The CD costs $15.24, including tax. Liz gives the store clerk a twenty-dollar bill. How much change should Liz get back?

You have $15.24 for the base cost, then you have to add tax (I'm assuming tax is 7%, that's what it is here).

To find tax, take 7% of $15 and add it to $15.24

$15*7% = $1.05 in tax.

$15.24 + $1.05 = $16.29 for the cost of the CD.

In order to find how much change Liz gets in return, subtract the total cost of the CD from $20.

$20.00 - $16.29 = $3.71 in change.