pile of sand is transported separately, and it takes 6 days for car A to be transported, and 9 days for car B to be transported. Now, after a few days of combined transport of the two cars, what (1/6) of this pile of sand is left? What is the correct column
一堆沙子单独运，甲车要6天运完，乙车要9天运完，现在两车合运几天后剩下这堆沙子的(1/6)？正确的列式是多少
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/6) + (1/9)</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">(5/6) / (5/18)</gadget>
<output>3</output>

<result>3</result>