A skirt originally cost $10. How much will it cost if you sell it in Amazon with 25% mark-up price

$20.40

Step-by-step explanation:

20% off means that the new price of the skirt will be 80% of the original price:

$30(100%  – 20%) = $30(80%)

Converting the percent to a decimal gives:

$30(0.8) = $24.00

There is an additional 15% off the sale price of $24.00, so the final price is 85% of the sale price:

$24(100%  – 15%) = $24(85%)

Again converting the percent to a decimal gives:

$24(0.85) = $20.40