How many degrees does the hour hand on the clock face rotate around the center of the clock face to go from 6:00 to 9:00.
钟面上的时针围绕钟面中心旋转多少度才能从6：00走到9：00．
<gadget id="calculator">9 - 6</gadget>
<output>3</output>

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

<result>90</result>