(2) It depends, because x>y, if z≠0, then Z? & gt0, so correct; If z=0, then xz? =yz？

(3) Transform the original formula, x=3/5(k+3), if x is non-negative, then k >；; -3

(4) If the result is always positive, remove the absolute value from the original formula: ①5x-3=3-5x, x = 3/5; ②-5x+3=3-5x=0, which is meaningless.

So x=3/5.