Expand a div to fill the remaining width

Question

I want a two-column div layout, where each one can have variable width e.g.

Answer 1

This is fairly easy using flexbox. See the snippet below. I've added a wrapper container to control flow and set a global height. Borders have been added as well to identify the elements. Notice that divs now expand to the full height as well, as required. Vendor prefixes should be used for flexbox in a real world scenario since is not yet fully supported.

I've developed a free tool to understand and design layouts using flexbox. Check it out here: http://algid.com/Flex-Designer

.container{
    height:180px;
    border:3px solid #00f;
    display:flex;
    align-items:stretch;
}
div {
    display:flex;
    border:3px solid #0f0;
}
.second {
    display:flex;
    flex-grow:1;
    border:3px solid #f00;
}

    
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