A and B practice running. A runs 7.5 meters per second, and B runs 7 meters per second. Now B runs for 10 seconds first. How many seconds later will A catch up with B?
甲、乙二人练习跑步，甲每秒跑7.5米，乙每秒7米，现在乙先跑10秒，几秒后甲追上乙？
<gadget id="calculator">7.5 - 7</gadget>
<output>0.5</output>

<gadget id="calculator">7 / 0.5</gadget>
<output>14</output>

<gadget id="calculator">10 * 14</gadget>
<output>140</output>

<result>140</result>