Use a commutative law to write an equivalent expression to xy + 3z?

The commutative law says the order of operands for addition or multiplication may be reversed without changing the value of the result. Thus, all of the following are equivalent
  xy + 3z
  yx + 3z
  xy + z*3
  yx + z*3
  3z + xy
  z*3 + xy
  3z + yx
  z*3 + yx

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I have used the asterisk (*) to indicate multiplication by a following numerical value to avoid ambiguity regarding the meaning of the 3. In other words, many people interpret z3 to mean z^3. Writing it as z*3 removes doubt.