500 * 25%
= 500*1/4
=125 1st time marked down.
Then, 500-125 = 375
375 * 25%
=375*1/4
=93.75 2nd time marked down.
Then, 375-93.75 = 281.25
281.25 * 25%
=281.25*1/4
=70.31 3rd time marked down.
Then, 281.25 - 70.31 = $210.94
The final price is $21.94