Beibei bought an eraser. It used to be 1 cm and 5 mm long, but 7 mm was used. How long is this eraser now?
贝贝买来一块橡皮，原来长1厘米5毫米，用去7毫米，现在这块橡皮有多长？
<gadget id="calculator">15 - 7</gadget>
<output>8</output>

<result>8</result>