Paco had 50 cookies. He ate 21 cookies and gave 11 of them to his friend. How many more cookies did he eat than those he gave to his friend?
Paco had 50 cookies. 
He ate 21 cookies. 
He gave 11 cookies to his friend. 

That means that he has 50 - 21 - 11 = 18 cookies left. 

So he ate 21 - 11 = 10 more cookies than he gave to his friend.