After a batch of rice is used (2/5), another 90 kg is transported in. At this time, the rice is the original (6/7). How many kilograms of rice did there originally have?
一批大米，用去(2/5)后，又运进90千克，这时的大米是原来的(6/7)，原来有大米多少千克？
<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(6/7) - (3/5)</gadget>
<output>9/35 = around 0.257143</output>

<gadget id="calculator">90 / (9/35)</gadget>
<output>350</output>

<result>350</result>