A $2000 watch was put on sale so that Mr. Rogers bought it at 75% of its original price. He then sold the watch to his friend at 120% of the price that he bought it. What is the percentage discount obtained by Mr. Roger's friend from the original price?
Mr. Roger bought the perfume at $2000 x 75/100 = $
<gadget id="calculator">2000*75/100</gadget>
<output>1_500</output>
1500.
He then sold it to his friend at $1500 x 120/100 = $
<gadget id="calculator">1500*120/100</gadget>
<output>1_800</output>
1800.
So, Mr. Roger's friend paid $2000 - $1800 = $
<gadget id="calculator">2000-1800</gadget>
<output>200</output>
200 less than the original price.
So, his friend got $200/$2000 x 100% = 
<gadget id="calculator">200/2000*100</gadget>
<output>10</output>
10% discount.

<result>10</result>