if the $400 coat has already been marketed down (you are left with 60% of the $400 which is 0.6 x 400 = 240). If you then have an additional 25% discount it would mean 75% of 240 which is 0.75 x 240 = 180
the effective percent discount would be 45% because as a fraction 180/400 = 9/20 or if you change it on your calculator using the S<>D button makes 0.45 as a decimal and to make it a percentage you just times by 100 and there you have your correct percentage
