The elder sister has 38 comic books, and the younger sister has 52 comic books. How many comic books should the elder sister give to the younger sister so that the younger sister has twice as many comic books as the older sister.
姐姐有连环画38本，妹妹有连环画52本，姐姐要给妹妹多少本连环画，才能使妹妹本数是姐姐的2倍．
<gadget id="calculator">38 + 52</gadget>
<output>90</output>

<gadget id="calculator">90 / 3</gadget>
<output>30</output>

<gadget id="calculator">38 - 30</gadget>
<output>8</output>

<result>8</result>