Werner installs custom sound systems in cars.If he installs seven systems per day,his total costs are $300.If he installs eight systems per day,his total costs are $400.Werner will install eight sound systems per day only if the eighth customer is willing to pay at least:
A)$300.
B)$400.
C)$100.
D)$50.

Question

Quizplus · Accepted Answer

Let's call the cost of installing one sound system "x". Then we can set up two equations based on the information given:

7x + 300 = total cost when installing 7 systems per day
8x + 400 = total cost when installing 8 systems per day

Subtracting the first equation from the second, we get:

x + 100 = cost of installing the 8th system

This tells us that in order for Werner to install 8 systems per day, he needs to make at least $100 on the 8th installation. Therefore, the answer is choice C.

Werner Installs Custom Sound Systems in Cars