A pen is 15.7 yuan, which is 1.5 yuan cheaper than a pencil case. How much does a pencil case cost?
一支钢笔15.7元，比一个文具盒便宜1.5元，一个文具盒要多少钱？
<gadget id="calculator">15.7 + 1.5</gadget>
<output>17.2</output>

<result>17.2</result>