A truck drives from City A to City B, traveling 50 kilometers per hour, and travels for 12 hours. When returning, it takes 4 hours less because of the increased speed. What is the velocity when returning?
一辆货车从甲城开往乙城，每小时行50千米，行驶了12小时，返回时由于速度提高了，少用了4小时．返回时的速度是多少？
<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<gadget id="calculator">12 / 8</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">50 * (3/2)</gadget>
<output>75</output>

<result>75</result>