Question: Can you give me some step-by-step instructions for this math problem: 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?
Answer: 
Mr. Roger bought the perfume at $2000 x 75/100 = $1500.
He then sold it to his friend at $1500 x 120/100 = $1800
So, Mr. Roger's friend paid $2000 - $1800 = $200 less than the original price.
So, his friend got $200/$2000 x 100% = 10% discount.