Answer:
Her change was: $3.5
Explanation:
Mary bought a shirt on sale for $15.00.
As the sales tax was 10%.
i.e. 10/100 × 15 = $1.5
so the sales tax on $15.00 was $1.5.
Hence, the total cost Mary had to pay to buy the shirt was:
$1.5 + $1.5 = $16.5
As Mary paid with a $20 bill, therefore the change can be calculated as
20 - 16.5 = $3.5.
Therefore, her change was: $3.5