Two people, A and B, are running a 100-meter race. When A reaches the finish line, B is 20 meters behind A. If A and B keep their speed constant, in order for A and B to reach the finish line at the same time, how much should A's starting line be moved backwards? rice.
甲乙两人进行百米赛跑，当甲到达终点时，乙在甲后面20米，如果甲乙两人的速度保持不变，要使甲乙两人同时到达终点，甲的起跑线要比原来向后移动多少米．
<gadget id="calculator">100 / 4</gadget>
<output>25</output>

<gadget id="calculator">5 * 25</gadget>
<output>125</output>

<gadget id="calculator">125 - 100</gadget>
<output>25</output>

<result>25</result>