[Part A]
company A -> A=30m+13
company B -> B=28m+15
A=company A
B=company B
m= number of mattresses
[Part B]
Price charged to clean 4 mattresses
company A= $133
company B= $127
Justification
A=30(4)+13 B=28(4)+15
A=120+13 B=112+15
A=133 B=127
Company B would charge less. Even though the y-intercept is higher, the slope has a lower value which makes company A grow at a faster rate.
[Part C]
If you use company B instead of company A to clean 7 mattresses you will save 12 dollars. The price to clean 7 mattresses with company A is 223 while company B costs 211.
Company A: A=30(7)+13=223
Company B: B=28(7)+15=211