Let n be unknown number, then 1/5 of this number is 1/5n. When you add these two numbers, you get

You know that this sum is equal to 24, so

1. Multiply this equation by 5:

2. Solve it:

Answer: n=20, correct choice is B.
Answer: 3 1/2 minutes
Step-by-step explanation:
A copy machine makes 24 copies per minute.
How long does it take to make 84 copies?
It takes 3 1/2 minutes to make 84 copies.
Answer:
a) 

b) 

If we want to minimize the cost then we should rent the Acme Truck company.
Step-by-step explanation:
Assuming the following questions.
(a) Find the daily cost of leasing from each company as a function of the number of miles driven and sketch the graph of these functions.
For the Ace truck we know that leases its 10-ft box truck at $20/day and $0.50/mi. So then f(x) representing the daily cost is given by:

Where x represent the number of miles driven
For the Acme Truck we know that leases a similar truck at $15/day and $0.55/mi, so then the g*x( representing daily cost would be given by:

Where x represent the miles driven.
We can see the plot on the figure attached.
(b) Which company should you rent a truck from for 1 day if you plan to drive 70 miles and wish to minimize cost?
If we replace the value x=70 for both functions we got:


If we want to minimize the cost then we should rent the Acme Truck company.
I think it would be commutative or associative because there is anything to distribute so it is NOT distributive