Old Lessons Mistake

In the old Lesson- Strategy- Silman's lessons in Strategy (1) the O'kelly-Najdorf game, When I played 10. ... Nxf2,it says 10...Nxf2?? loses a piece after 11.Rf1, pinning the Knight to its Queen. But the Queen is hanging on c2!

You are quite right! I've analysed this position on my ChessBase 15, and indeed, 10. ... xf2 is a perfectly sound move. Although so, I think this shouldn't refrain you from finding the best and accurate move to complete this lesson. Chess.com workers should take note of this to provide computer-based analysis for each move to avoid misunderstandings or wrong "chess logic" being learned by beginner players. Thanks, rajesht1306 for mentioning this problem! 
*P.S. I'm just a passer-by commenting on this, you'll still need to wait for a worker to assist you.

Bump... let's see if a mod can come in here.

We are slowing working though these and converting them into our new lesson format. These kinds of mistakes will be solved as we do that. 

Thank You!!