Question

what happens when black hole and white hole come nearby?

Answer 1

There is nothing like White hole. It is fictional

Answer 2

Black hole:-

A black hole is a region of space time where gravity is so strong that nothing-no particles or even electromagnetic radiation such as light-can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a blackhole.

White hole:-

In generally relativity,a white hole is a hypothetical region of spacetime and singularity which cannot be entered from the outside , although energymatter,light and information can escape from it. White holes appear in the theory of eternal black holes.