A project alone takes 5 hours to complete and B takes 4 hours to complete alone. Now A and B have worked together for 2 hours, and there are still 2 kilometers left to be completed. Q: How many kilometers is this project in total?
一项工程，甲单独完成需要5小时，乙单独完成需要4小时．现甲，乙两人合作2小时，还剩2千米没有完成．问：这项工程总共有多少千米？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">2 / (1/10)</gadget>
<output>20</output>

<result>20</result>