An engineering team repaired one-third in 18 days. If the efficiency is increased by one-fifth after three days, how many days will it take to complete half of it?
一个工程队18天修了三分之一，如果做了3天后，效率提高五分之一，一共要多少天完成一半．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) / 18</gadget>
<output>1/54 = around 0.018519</output>

<gadget id="calculator">(1/54) * 3</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(1/2) - (1/18)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">(1/54) * (6/5)</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">(4/9) / (1/45)</gadget>
<output>20</output>

<gadget id="calculator">20 + 3</gadget>
<output>23</output>

<result>23</result>