HELP ME!

I do not know how to help mey daughter with her "The Cell Phone Dilemma" worksheet which asks her to create an equation offering the following info:

"You are going to buy a new cell phone. You are trying to decide between the ne IPhone 5 or the older model but still quite nice, IPhone 4. The following chart is the data given to you to help you make your decision.

PRICE IPhone4 IPhone5

$100 3000 0

$200 2400 400

$400 1200 1200

$600 0 2000

Write equations algebraically for each situation. You must show your work for this process.

Can someone help expalin to me how to equate an equation with these figures so that I can help my daughter?

Thank you