Tying images to one another and scaling?

I have an application that needs to scale an image in relation to another image due to different screen size, I have an image that is essentially a background that matches the width of开发者_运维百科 the screen and another image in a relative layout that is aligned so it fits on my phone in 2.2 but when seen on 2.1 Or ... i could just use something that scales the image as a percentage. Suggestions? edit: I guess all i need is to know how i can keep an image in a spot relative to another using relative layout and scale it through a percentage, different screen size will scale the other image but not this one because the other image fills the parent so when the screen size is smaller it just scales it down, however the one i need to scale does not because it doesn not fill the parent.