How to subrtact a negative from a negative?

Based on the figures as marked, /\rqs = —

If the simple annual interest rate on a loan is 6, what is the interest rate in percentage per month?

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.