Next year, Dana will be twice as old as her sister will be. Four years ago, Dana was three
times as old as her sister was. How old is each now?

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.