For a project, the ratio of completed to unfinished is 2:3, and after 200 more projects, the ratio of completed to unfinished is 3:4. How many does this project have to do in total?
一项工程，已完成与未完成的比是2：3，再做200个后，已完成与未完成的比是3：4．这项工程共要做多少个？
<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">2 + 3</gadget>
<output>5</output>

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

<gadget id="calculator">(3/7) - (2/5)</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">200 / (1/35)</gadget>
<output>7_000</output>

<result>7_000</result>