/* Wiki全体：画面幅の90% */
body > div.uk-container.uk-container-center {
    width: 90%;
    max-width: none;
}

/* 本文：全体幅から左メニュー分を引く */
body > div.uk-container.uk-container-center
> div.uk-grid
> div[class*=uk-width-].main_content {
    width: calc(100% - 230px);
}