The elder sister has 18.7 yuan. After giving the younger sister 3.5 yuan, the amount of money is exactly the same. How much money does the younger sister have?
姐姐有18.7元，给妹妹3.5元后两人钱数正好相等，妹妹原来有多少钱？
<gadget id="calculator">3.5 * 2</gadget>
<output>7</output>

<gadget id="calculator">18.7 - 7</gadget>
<output>11.7</output>

<result>11.7</result>