Question

why (x,y) is not equal (y,x)​

Answer 1

The expression xy can be used in a variety of situation for different kinds of mathematical objects (not only to numbers!) and operations on them, and in many (if not in most) situations xy is not equal yx.

Let x and y be two processes or operations and xy is the outcome of their consecutive application: first x, then y. A kindergarten level “real life” example:

x is putting a sock on the left foot and y is putting a sock on the right foot; very obviously, the order of operation does not matter, xy = yx.

x is putting a sock on the left foot and y is putting a boot on the same foot. You would perhaps agree that xy ≠ yx.