project can be completed in 12 hours by A alone, and 10 hours by B alone. After A and B have worked together for 3 hours, what fraction of the project is left unfinished?
一项工程，甲独做需12小时完成，乙独做需10小时完成，甲、乙两人合作了3小时后，还剩这项工程的几分之几没有完成？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/12) + (1/10)</gadget>
<output>11/60 = around 0.183333</output>

<gadget id="calculator">(11/60) * 3</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">1 - (11/20)</gadget>
<output>9/20 = around 0.45</output>

<result>9/20 = around 0.45</result>