How many degrees does the hour hand on the clock face rotate from 6:00 to 9:00?
钟面上的时针从6：00到9：00旋转了多少°．
<gadget id="calculator">9 - 6</gadget>
<output>3</output>

<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<result>90</result>