One of the largest flowers, the Rafflesia, weighs about 15 lb. How many Rafflesia flowers can be placed in a container that can hold a maximum of 240 lb?

Lets use R as the number of flowers to be carried. (Or whatever letter you like)
R = number of flowers to be carried. 

Multiply 15r
15r = 240
This can also be expressed as 15 pounds per flower times number of flowers equals 240 pounds.
15f = 240 (15 pounds per flower times number of flowers equals 240 pounds) 

Divide 240 by 15 to get r
 R = 16 flowers 

Hope this helped :)