(2/9) plus a number is equal to the difference between 1 and (7/18), what is this number?
(2/9)加上一个数等于1与(7/18)的差，这个数是多少？
<gadget id="calculator">7 / 18</gadget>
<output>7/18 = around 0.388889</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">1 - (7/18) - (2/9)</gadget>
<output>7/18 = around 0.388889</output>

<result>7/18 = around 0.388889</result>