A dairy farm has 25 cows and 15 calves, each cow grazes 12 kg of grass per day, and each calf grazes 6 kg of grass per day. The existing grass is 7020 kg, how many days can they eat?
一个奶牛场有25头奶牛和15头小牛，每头奶牛每天吃草12千克，每头小牛每天吃草6千克．现有草7020千克，可供它们吃多少天？
<gadget id="calculator">25 * 12</gadget>
<output>300</output>

<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">300 + 90</gadget>
<output>390</output>

<gadget id="calculator">7_020 / 390</gadget>
<output>18</output>

<result>18</result>