A and B are running a 60-meter race. When A reaches the finish line, B is 20 meters behind A. If the respective speeds of the two remain the same, in order for A and B to reach the finish line at the same time, how many meters should A's starting line be moved back from the original starting line?
甲、乙两人进行60米赛跑．当甲到达终点时，乙在甲后面20米，如果两人各自速度不变，要使甲、乙两人同时到达终点，甲的起跑线应比原起跑线后移多少米？
<gadget id="calculator">60 - 20</gadget>
<output>40</output>

<gadget id="calculator">60 / 40</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">60 * (3/2)</gadget>
<output>90</output>

<gadget id="calculator">90 - 60</gadget>
<output>30</output>

<result>30</result>