The rice stored in the grain store is flour (4/5). When 30 tons of rice and 25% of the flour are sold, the remaining flour is equal to the rice. How many tons of flour are in stock?
粮店库存的大米是面粉的(4/5)，当卖出30吨大米和25%的面粉后，剩下的面粉和大米相等，原来库存面粉多少吨？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) - 1</gadget>
<output>-3/4 = around -0.75</output>

<gadget id="calculator">(4/5) + (-3/4)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">30 / (1/20)</gadget>
<output>600</output>

<result>600</result>