The elder sister gave the younger sister 4 exercise books, and they were 4 more than the younger sister. How many fewer books did the younger sister have than the older sister?
姐姐送给妹妹4本练习本，还比妹妹多4本，妹妹原来比姐姐少几本？
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">8 + 4</gadget>
<output>12</output>

<result>12</result>