The distance between the two places is 900 kilometers, and it takes 15 days for A to travel, and 12 days for B to travel. Now A leaves for 2 days first, and B goes after A. Ask how many kilometers to go to catch up?
两地相距900千米，甲走需15天，乙走需12天．现在甲先出发2天，乙去追甲．问要走多少千米才可追上？
<gadget id="calculator">900 / 12</gadget>
<output>75</output>

<gadget id="calculator">900 / 15</gadget>
<output>60</output>

<gadget id="calculator">75 - 60</gadget>
<output>15</output>

<gadget id="calculator">120 / 15</gadget>
<output>8</output>

<gadget id="calculator">75 * 8</gadget>
<output>600</output>

<result>600</result>