There are 30 red balls and 150 white balls, how much less red balls than white balls.
红球有30个，白球有150个，红球比白球少多少．
<gadget id="calculator">150 - 30</gadget>
<output>120</output>

<gadget id="calculator">120 / 150</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>