A, B, and C all make 20 of the same parts and start to make them at the same time. When A is finished, B only makes 16 parts, and C makes 12 parts. When B finished, how many C left to do.
甲、乙、丙三人都做同样的零件20个，同时开始做，当甲完成时乙只做了16个，丙做了12个．当乙做完时，丙还有多少个没有做．
<gadget id="calculator">16 / 12</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">1 / (4/3)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">20 * (3/4)</gadget>
<output>15</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<result>5</result>