EDIT: DUMB. I just saw the "Pre-Algebra and Algebra" section included functions. Sorry!

Hi! I'm a grade 11 student preparing for my winter exams, and I've come across two questions that I can't seem to solve. Any help would be greatly appreciated.

1) A small company produces and sells x widgets per week. They find that their cost function in dollars is C(x)=$50+3x and their revenue function in dollars is R(x)=6x-(x^2/100). How many widgets per week should be produced for maximum profits?

I attempted to do 6x-(x^2/100)=$50+3x, then got (x^2/100)+3x-50=0 and used the quadratic equation. I got the wrong answer, so I'm assuming I made a no-no in making the two functions equal each other. What are you supposed to do, if you don't mind explaining?

The second one is more confusing.

2)A rectangular field is to be enclosed by a fence. Two fences, parallel to one side of the field, divide the field into three rectangular fields. If 2400 m of fence are available, find the dimensions giving the maximum area.

I don't really understand how to get the answer here. Am I supposed to find the dimensions for the maximum area of the field?

Thank you!