Final answer:
The percent of decrease in the cost of Debbie's school uniform is 5%, calculated by dividing the price decrease of $3 by the original price of $60 and then multiplying by 100.
Step-by-step explanation:
To calculate the percent of decrease in the cost of Debbie's school uniform, we can use the formula for percentage decrease, which is: (original price - new price) / original price * 100%. In this case, the original price is $60, and the new price is $57.
First, find the difference in price:
- Price decrease = $60 - $57 = $3
Next, divide the price decrease by the original price and multiply by 100 to find the percentage:
- Percent of decrease = ($3 / $60) * 100% = 5%
Therefore, the percent of decrease in the cost of the uniform is 5%, which corresponds to option b.