Please help how do i solve this

The sum of two numbers is 86, and their difference is 20. find the two numbers

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.

Write an equation of the line that passes through 9,2 and is parallel to the line y=5/3x+9