19 children line up, there are 7 classmates in front of Lili, how many classmates are behind Lili? How many
19个小朋友排队，丽丽的前面有7个同学，丽丽的后面有几个同学？多少
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<gadget id="calculator">19 - 8</gadget>
<output>11</output>

<result>11</result>