It takes 320 rose petals to make an ounce of perfume. If each rose produces 8 petals, and there are 12 roses per bush, how many bushes will Fern have to harvest to make 20 12-ounce bottles of perfume?
First find the number of roses needed for one ounce of perfume: 320 petals / 8 petals/rose = 
<gadget id="calculator">320/8</gadget>
<output>40</output>
40 roses.
Then multiply the number of roses needed for one ounce by the number of ounces per bottle to find the number of roses per bottle: 40 roses/ounce * 12 ounces/bottle = 
<gadget id="calculator">40*12</gadget>
<output>480</output>
480 roses/bottle.
Then multiply that number by the number of bottles to find the total number of roses needed: 480 roses/bottle * 20 bottles = 9600 roses.
Then divide that number by the number of roses per bush to find the number of bushes Fern needs to harvest: 9600 roses / 12 roses/bush = 
<gadget id="calculator">9600/12</gadget>
<output>800</output>
800 bushes.

<result>800</result>