first: any number, minus zero (-0) and divided by one (/1) would be the same. that´s why I´ve asked you why they were there.
second: you got everything upside-down. that line:
_root.xnew = _root.mask2._x+(4-1)*100/2;
means:
[SIZE=1]new position on x axisIS EQUAL TOmask2 position on x axisplus (4-1)multiplied by****100 divided by2 [/SIZE]
or:
[SIZE=1]new position on x axisIS EQUAL TOmask2 position on x axisplus150;[/SIZE]
so, it is a number. what you have to do is to find the nuber (VALUE) of the position on the X axis that you want to place your object and use it there. Perhaps if you post your fla here I can be of better help :-\