The weight of a cow grazing in a day is equal to the weight of a rabbit grazing in 9 days, and it is also equal to the weight of 6 sheep grazing in a day. It is known that a cow eats 18 kg of grass a day, and a rabbit and a sheep can eat 18 kg of grass a day. How many kilograms of grass do you eat?
一头牛一天吃草的重量和一只兔子9天吃草的重量相等，也和6只羊一天吃草的重量相等，已知一头牛一天吃青草18千克，一只兔子和一只羊一天共吃青草多少千克？
<gadget id="calculator">18 / 9</gadget>
<output>2</output>

<gadget id="calculator">18 / 6</gadget>
<output>3</output>

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<result>5</result>