2 Crab Generals and 4 Shrimp Soldiers can clean the Dragon Palace (3/10), 8 Crab Generals and 10 Shrimp Soldiers can clean up the entire Dragon Palace. If only the crab generals are used to clean, compared with the shrimp soldiers alone, how many more shrimp soldiers than crab generals are needed to clean the entire Dragon Palace?
2个蟹将和4个虾兵能打扫龙宫的(3/10)，8个蟹将和10个虾兵就能打扫完全部龙宫．如果是单让蟹将去打扫，与单让虾兵去打扫进行比较，那么要打扫完全部龙宫，虾兵比蟹将要多多少个．
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / (1/12)</gadget>
<output>12</output>

<gadget id="calculator">30 - 12</gadget>
<output>18</output>

<result>18</result>