The farmer said: "If you sell 75 chickens, then the chicken feed can last for 20 days; if you buy another 100 chickens, then the chicken feed can only last for 15 days." How many chickens did the farmer raise?
农夫说："如果卖掉75只鸡，那么鸡饲料可以维持20天；如果再买进100只鸡，那么鸡饲料只能维持15天．"农夫养了多少只鸡．
<gadget id="calculator">100 + 75</gadget>
<output>175</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/15) - (1/20)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">175 / (1/60)</gadget>
<output>10_500</output>

<gadget id="calculator">10_500 / 20</gadget>
<output>525</output>

<gadget id="calculator">525 + 75</gadget>
<output>600</output>

<result>600</result>