Mr. Grey had a $100 000 x 10/100 = $<<100000*10/100=10000>>10,000 profit.
So, Mr. Grey sold the house to Mr. Brown for $100 000 + $10 000 = $<<100000+10000=110000>>110,000.
Mr. Brown sold the house $110 000 x 10/100 = $<<110000*10/100=11000>>11,000 less than its purchased price.
Thus, Mr. Brown sold it for $110 000 - $11 000 = $99,000 to his friend.
#### 99000