If 3 cows and 2 horses graze 80 kg of grass per day, and 5 cows and 4 horses graze 140 kg of grass per day, then how many kg of grass do each cow and each horse graze on average per day?
3头牛和2匹马每天吃草80千克，5头牛和4匹马每天吃草140千克，则每头牛和每匹马平均一天共吃草多少千克．
<gadget id="calculator">140 - 80</gadget>
<output>60</output>

<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<result>30</result>