A 24-kilometer-long road needs to be built. 4 kilometers are built on the first day, and the rest (3/8) is repaired on the second day. How many kilometers are left to be repaired?
要修一段长24千米的路，第一天修了4千米，第二天修了余下的(3/8)，还剩下多少千米没有修完？
<gadget id="calculator">24 - 4</gadget>
<output>20</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">20 * (3/8)</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">24 - (15/2) - 4</gadget>
<output>25/2 = around 12.5</output>

<result>25/2 = around 12.5</result>