For this case you want to know what percentage of the original price the customer paid for a specific shirt.
If the original price was $ 80 and payment $ 40, we have the following rule of three:
80 ----------> 100%
40 ----------> x
Where "x" represents the percentage that the customer paid with respect to the original price.
[tex]x = \frac {40 * 100} {80}\\x = 50[/tex]
Thus, the customer paid 50% of the original price of the shirt.
Answer:
50%
