let x=(4,6,8) y=(2,3,16) R(x,y) means x divide by y
∀x (∃y R(x, y))= means every x divide by some y which is hold true in our assumption (here 2 divide every x)
∃y (∃x R(x, y))= means some y divide by some x which is also hold true(here 16 divide by 4 or 8)