At the beginning of school, Mai went to the stationery store and bought a pen and a pencil case. A pen was 12.6 yuan, which was 3.6 yuan more expensive than the pencil case. How much is a stationery box?
开学初，小麦到文具店买了一枝钢笔和一个文具盒，一支钢笔12.6元，比文具盒贵3.6元．一个文具盒多少钱？
<gadget id="calculator">12.6 - 3.6</gadget>
<output>9</output>

<result>9</result>