Obviously the glasses used to be 300 degrees, but now the glasses are 150 degrees. How much is the degree of the glasses reduced?
明明眼镜原来300度，现在眼镜是150度，明明眼镜度数减少了多少度．
<gadget id="calculator">300 - 150</gadget>
<output>150</output>

<result>150</result>