3 cows and 6 sheep eat a total of 93 kg of grass a day. 6 cows and 5 sheep eat a total of 130 kg of grass a day. How much more grass does each cow eat per day than each sheep?
3头牛和6只羊一天共吃草93千克．6头牛和5只羊，一天共吃草130千克．每头牛每天比每只羊多吃草多少千克？
<gadget id="calculator">15 - 8</gadget>
<output>7</output>

<result>7</result>