Three cows and eight sheep eat a total of 48 kilograms of grass a day; five cows and fifteen sheep eat a total of 85 kilograms of grass a day. How many kilograms of grass do a cow and a sheep eat together in a day?
三头牛和八只羊，一天共吃青草48千克；五头牛和十五只羊一天共吃青草85千克．一头牛和一只羊一天共吃青草多少千克？
<gadget id="calculator">85 * 3</gadget>
<output>255</output>

<gadget id="calculator">48 * 5</gadget>
<output>240</output>

<gadget id="calculator">255 - 240</gadget>
<output>15</output>

<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<gadget id="calculator">45 - 40</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">3 * 8</gadget>
<output>24</output>

<gadget id="calculator">48 - 24</gadget>
<output>24</output>

<gadget id="calculator">24 / 3</gadget>
<output>8</output>

<gadget id="calculator">3 + 8</gadget>
<output>11</output>

<result>11</result>