The ratio of goods stored in warehouses A and B is 7:5. If 650 tons of goods are transported from warehouse A to warehouse B, the ratio of goods in the two warehouses is 3:4. How many tons of goods are there in warehouse A?
A、B两个仓库存有货物的比是7：5，如果从A仓库运走650吨货物到B仓库，那么两个仓库的货物比是3：4，A仓库原有货物多少吨？
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(7/12) - (3/7)</gadget>
<output>13/84 = around 0.154762</output>

<gadget id="calculator">650 / (13/84)</gadget>
<output>4_200</output>

<gadget id="calculator">4_200 * (7/12)</gadget>
<output>2_450</output>

<result>2_450</result>