This question can be solved using an "is/of" equation.
To find how much the shirt has been marked down, you must first ask the question, "what IS 33% OF $25?"
The is/of equation is as follows:
is / of = % / 100
Since we do not know what 33% of $25 is, we will use the variable x.
Plugging in the information we get:
x / 25 = 33 / 100
Then you cross multiply x over 25 with 33 over 100.
So,
25 x 33 = 100x
825 = 100x
825 / 100 = x
8.25 = x
Your result is 8.25. This means that the shirt's price was brought down from the original price by $8.25. All you have to do now is subtract $8.25 from $25.
25.00 - 8.25 = 16.75
The sale price of a shirt that was originally $25 but that has been marked down by 33% will cost $16.75.