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

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.

xy + 3z

yx + 3z

xy + z*3

yx + z*3

3z + xy

z*3 + xy

3z + yx

z*3 + yx

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.