Answer:
He paid $15.
Step-by-step explanation:
Store bough each shirt for $20.
It raised the price of the shirt by 50%.
50% of $20 = 0.2 × $20 = $10
$20 + $10 = $30
The store sold the shirts at a regular price of $30.
The store then had a sale at 50% off.
50% of $30 = 0.5 × $30 = $15
$30 - $15 = $15
The sale price was $15.
