What is the sum of the simplest proper fractions whose denominator is 18?
分母是18的最简真分数的和是多少．
<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">5 / 18</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">7 / 18</gadget>
<output>7/18 = around 0.388889</output>

<gadget id="calculator">11 / 18</gadget>
<output>11/18 = around 0.611111</output>

<gadget id="calculator">13 / 18</gadget>
<output>13/18 = around 0.722222</output>

<gadget id="calculator">17 / 18</gadget>
<output>17/18 = around 0.944444</output>

<gadget id="calculator">(1/18) + (5/18) + (7/18) + (11/18) + (13/18) + (17/18)</gadget>
<output>3</output>

<result>3</result>