Answer:
$24
Step-by-step explanation:
Let the full price of $30 be 100%.
If the discount allowed is 20%, then the percentage of the original price that a customer will pay is:
[tex]P=100\%-20\%\\P=80\%[/tex]
80% of a marked price of $30 is:
[tex]80\%*\$30\\\$24[/tex]
A customer will pay $24.