concept-grid-3.html

<div class="row">
    <div class="col-xs-6 blue">
        1
    </div>
    <div class="col-xs-6">
        <div class="row">
            <div class="col-xs-3 green">
                2a
            </div>
            <div class="col-xs-9 orange">
                2b
            </div>
            <div class="col-xs-7 orange">
                2c
            </div>
            <div class="col-xs-5 green">
                2d
            </div>
        </div>
    </div>
</div>