It takes 12 days for A to complete a project alone, and 15 days for B to complete the same project alone. How much of the remaining project will be left after the two work together for 6 days?
甲单独做一项工程要12天完成，乙单独做同样的工程要15天完成，先两人合作6天后还剩工程的多少
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/12) + (1/15)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">6 * (3/20)</gadget>
<output>9/10 = around 0.9</output>

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

<result>1/10 = around 0.1</result>