A, B, and C are running a race, and the speed of the three remains unchanged. When A reaches the finish line, B still has 20 meters left. C still has 30 meters left. When B arrives, C still has 15 meters left. How many meters is this race?
甲乙丙三人进行赛跑，三人的速度保持不变，甲到终点时，乙还有20米．丙还有30米，当乙到时，丙还有15米，这是多少米的赛跑．
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<gadget id="calculator">20 * 30</gadget>
<output>600</output>

<gadget id="calculator">600 - 600</gadget>
<output>0</output>

<gadget id="calculator">300 + 0</gadget>
<output>300</output>

<gadget id="calculator">20 - 30</gadget>
<output>-10</output>

<gadget id="calculator">15 + (-10)</gadget>
<output>5</output>

<gadget id="calculator">300 / 5</gadget>
<output>60</output>

<result>60</result>