a. Algebraic equation.
As the problem states, we have two plans: Plan A and Plan B. In this question, we will use Plan B to write an equation from the graph. We can write an equation having two points. Thus, from the graph, we know the two points:
[tex]P_{1}(0,20) \ and \ P_{2}=(140,70)[/tex]
Therefore, the equation of a straight line is:
[tex]y-y_{0}=m(x-x_{0})[/tex]
[tex]y-y_{0}=m(x-x_{0}) \\ \\ y-20=\frac{70-20}{140-0}(x-0) \\ \\ \boxed{y=\frac{5}{14}x+20}[/tex]
b. Graph.
For Plan B we know that it offers a fixed payment of $30 plus 25¢ per mile. We know that 1¢ is equivalent to $0,01, therefore 25¢ = $0,25. Therefore, we can write the plan as a fixed payment of $30 plus $0,25 per mile. This can be written using the following equation:
[tex]\boxed{y=0,25x+30}[/tex]
So the graph is shown below.
c. Explanation.
The line in red represents [tex]y=\frac{5}{14}x+20}[/tex] while the line in blue represents [tex]y=0,25x+30[/tex]. Both Plans offer a fixed payment plus an extra fee per mile. If Trey runs less than 93,333 miles, he needs to rent Plan A because the cost here is less than Plan B. On the other hand, if he runs more than 93,333 miles, he needs to choose Plan B rather than Plan A because the cost of Plan B is less than the cost of Plan A here.
d. Same total cost.
The same total cost occurs when both line intersect, that is, at the point [tex](93.333, 53.333)[/tex]. Hence if Trey runs exactly 93,333 miles, he'll need to pay 53,333$. Therefore, in this situation no matter what plan he chooses because he will pay the same amount of money.