Question

in what way is data hiding related to data abstraction

Answer 1

Data abstraction is to represent essential features of the data without getting involved with the complexity of the entire data.
This means data abstraction shows only the essential features and it hides the other part of the data.

Thus, data hiding in one way is same as data abstraction. 

Answer 2

Data abstraction focuses on the observable behavior of an object. But Data hiding(encapsulation) focuses upon the implementation that gives rise to this behavior.
Hope it will help