Why do we say:“Are you any good at painting”? (Sec 1 WB, page 9, Ex. 3)
 

Why do we say:“Are you any good at painting”? (Sec 1 WB, page 9, Ex. 3)
Here, any is an adverb that means “to any extent, in any degree, at all”. When we ask if someone is any good, we are asking if they are even a little bit good. If we want to know if someone really is good, we ask simply “Are you good at ...?”
...............................................

Are you a good student ...........English ?
a-at b-in c--of `