[twenty eleven] can't widen pages / theme

Hi there

I have been trying to widen my site via stylesheet of the child theme. I am at https://www.nadaav.com/n

But I can’t seem to widen it beyond approx 1000px. I only want to widen it by about another 100 but can’t seem to manage. I tried this code, which I saw on the forums elsewhere:

#page {
    margin: 2em auto;
    max-width: 1200x;
}

.singular .entry-header,
.singular .entry-content,
.singular footer.entry-meta,
.singular #comments-title {
    width: 90%;
}

The content / text area width did increase within the page but the overall page width has remained. It causes me a problem on this page in particular: https://nadaav.com/n/films/showreels/ where I wold like the screens to sit three abreast.

I’d really appreciate any thoughts as to whats causing the problem – is it possible some other code in my style sheet is preventing the widening?

thanks kindly