Super easy I just suck at math

In a class, there are 12 girls. if the ratio of boys to girls is 5: 4 how many boys are there in the class

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.

If a company produces x units of an item at a cost of $35 apiece the function c=35x is a of the total production costs