Supply — How do I make all my pages dynamic full-width, just like the homepage

I'm using the Supply theme where I assign one page as my Homepage, and I have the option of making it a Full Width Homepage in the Style Editor. My homepage sizes dynamically, and looks good across all platforms. I'd like to make ALL my pages dynamic full width, just like the homepage.

I've tried using CSS code mainx { width: 1020px } which works fine, but is not dynamic, and the pages look terrible on tablets and phones.

I would be grateful if someone could suggest some code that would give my pages dynamic full width.

Thanks much.

I tried

#main {width: auto} 

and it seems to have worked.

THANKS SO MUCH!

THANKS!This what worked for me:

PAGES > Click on the wheel of each page, upper right corner click advanced, insert:

I am trying to do this in my York website for my pages, and I can't get it to work. Here is our website, www.schickeldesign.com. I want my regular pages to be full width like my gallery and index pages. Any insight?