How much salt is in a mixture containing 10 gallons of an 11% salt solution and 6 gallons of a 7% salt solution

Asmall business produces and sells balls. the fixed costs are $20 and each ball costs $4.32 to produce. each ball sells for $8.32. write the equations for the total cost, c, and the revenue, r, then use the graphing method to determine how many balls must be sold to break even.

Which one is the correct answer, and why?

Ireally don't understand this, i'm really an idiot but i want to know how to figure this out. !