A, B and C are running a 60m race at an even speed. When A crosses the finish line, he is 10m ahead of B and 20m ahead of C. When B reaches the finish line, how much ahead is C?
甲乙丙三人都以均匀的速度进行60m赛跑，当甲冲过终点时，比乙领先10m，比丙领先20m，当乙到达终点时，比丙领先多少？
<gadget id="calculator">60 * 60</gadget>
<output>3_600</output>

<gadget id="calculator">60 * 20</gadget>
<output>1_200</output>

<gadget id="calculator">3_600 - 1_200</gadget>
<output>2_400</output>

<gadget id="calculator">60 - 10</gadget>
<output>50</output>

<gadget id="calculator">2_400 / 50</gadget>
<output>48</output>

<gadget id="calculator">60 - 48</gadget>
<output>12</output>

<result>12</result>