<div class="layout4">
  <div class="floatContent">
    超长文字超长文字超长文字超长文字超长文字超长文字超长文字超长文字
  </div>
  <div class="floatFix">
    定长文字
  </div>
</div>
@contentWidth:100px;
@contentMarginRight: 20px;
@minusNumber: @contentWidth + @contentMarginRight;

.layout4{
  width: 30%;
  background: red;
  overflow: hidden;
  
  .floatContent{
    width: calc(~"100% - @{minusNumber}");
    overflow:hidden;
    text-overflow:ellipsis;
    white-space: nowrap;
    float: left;
  }
  
  .floatFix{
    float: right;
    text-align:right;
    width: contentWidth;
  }
}
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