Why living beings like / dislike things in the world? All living beings (animals + humans) like something, and they don't like some another things? What is the reason for liking and disliking. 
Eg: Imagine there are two best friends let's call friend A and friend B. Friend A likes a lady call X (very pretty lady) meanwhile friend B doesn't like lady X. What's the reason according to the buddhism.

To narrow down the question the point is though lady X is very pretty for friend A but not for friend B. Why is it?
Upasaka Isuru Gunawardana,

Touched by an pleasing object on the senses, and unwise thinking (avijjā, or improper attention) is the cause that greed arises.

Touched by an unpleasing object on the senses, and unwise thinking (avijjā, or improper attention) is the cause that aversion arises.

In short avijjā-phassa is the cause of domanassa, somanassa and indifferent mindstates, feelings. Good to keep in mind that the third is actually often miss-discriminated as real equanimity, beyond householder-equanimity.

(Note that this is not given for trade, exchange, stacks or entertainment but for release from this bonds in the world)