class里包含两个类，用less的嵌套怎么写呢？？

                        <div class="row row-wrap">                            <div class="col-xs-9 xm-title ">                                <span>SECRET系列的产品</span>                            </div>                            <div class="col-xs-3 xm-state-on">                                <span>已付款</span>                            </div>                        </div>

像上边的row row-wrap怎么接下边的col-xs-9 xm-title呢？真心求教