Lei Lei collected 20 more stamps than Ming Ming, who obviously collected Lei Lei's (3/4), and Ming Ming collected how many stamps.
雷雷收集的邮票比明明多20枚，明明收集的是雷雷的(3/4)，明明收藏了多少枚邮票．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 / (1/4)</gadget>
<output>80</output>

<gadget id="calculator">80 * (3/4)</gadget>
<output>60</output>

<result>60</result>