A fraction is 1 after adding one of its fractional units, and 8/9 after subtracting one of its fractional units. What is this fraction?
一个分数，加上它的一个分数单位后是1，减去它的一个分数单位后是8/9，这个分数是多少？
<gadget id="calculator">8 / 9</gadget>
<output>8/9 = around 0.888889</output>

<gadget id="calculator">1 - (8/9)</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/9) / 2</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">1 - (1/18)</gadget>
<output>17/18 = around 0.944444</output>

<result>17/18 = around 0.944444</result>