math
posted by Daniel .
1) A rancher wants to enclose two rectangular areas near a river, one for sheep and one for cattle. There is 240m of fencing available. Express the area of the enclosures as a function of its dimension.
2) A container company is designing on opentop, squarebased, rectangular box that will have a volume of 62.5 cm^3 [cubed]. Express the surface area of the box as a function of its width.
3) An apple farm yields an average of 30 bushels of apples per tree when 20 trees are planted on an acre of ground. Each time 1 more tree is planted per acre, the yield decreases 1 bushel per tree due to the extra congestion. Express the total yield as a function of the number of trees planted.
4) Express the area of an equilateral triangle as a function of the length of one side.

looks like "homework dumping" or an assignment is due looking at the different types of questions.
Exactly where are your difficulties?
What have you got so far? 
This is for calculus and its a practice assignment. I need a howto on solving these.
Each answer must be a function. 
it would be appreciated