How do I solve this?

What could explain what happened when the time was equal to 120 minutes

F(x)=x/2-2 and g(x)=2x^2+x-3 find (f+g)(x)

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.