Adjectives as qualifiers

Solution 1:

Grammatically, "well-known" qualifies "writer". You can tell this since they are placed in juxtaposition in the order adjective->noun, the usual method in English.

Semantically, "well-known" might be understood to qualify both to some extent, since the copula "is" equates the two. However, consider that:

The well-known Ruskin Bond is a writer

does not mean the same thing. Your sentence means "among writers, Ruskin Bond is well known." My sentence means "Ruskin Bond is well known, and happens to be a writer."

Solution 2:

If I recall my grammar-school grammar, writer is a predicate nominative and is roughly equated by "is" to the subject, Ruskin-Bond. However the connection is not an exact identity.

As phrased, well-known appears to modify writer, both because of its proximity and because it follows the article "a" which clearly refers to writer.

In other constructions it could be different.

The well-known Ruskin-Bond is a little-known expert carpenter.