C. Zero slope. If it's going straight up and down, there is no slope.
-19.2
12/(-5/8) means 12*(-8/5)
12*8=96
96/5=19.2
don’t forget the negative sign
so
-19.2
I believe the numbers are 63 and 65.
I will be including both an basic explanation of what it is and its proof.
I'm guessing you are either learning about conditional probability at school or preparing for competitions.
Baye's theorem states:

That is the theorem itself and it means that the probability that event A happens given B is true equals the probability event B happens given A is true times the probability event A happens divided by the probability B happens.
That was the basic of the theorem and the proof of this is basically just testing how well you understand what conditional probability is.


Now we know that the probably that A and B both happens is the same as the probably that B and A both happens.
Therefore P(A|B) can be seen as P(B|A) multiplied by P(A) and then divided by P(B) which gives the right hand side of the first equation. And this is basically the theorem.

**Note P(B) have to be not equal to 0 because having a 0 in the denominator would make this equation undefined.
If you have any questions or need further explanations please ask me in the comments of the answer, I hope this helped!
Answer:
Part a) 
Part b) 
Part c) Standard Daily Rate plus Mileage plan
Step-by-step explanation:
Part a) What would be the cost of the Standard Daily Rate plus Mileage plan?
Let
y ----> the total cost
x ----> the number of kilometers
we have that
For a Luxury car

For x=400 km
substitute


Part b) What would be the cost of the Unlimited Mileage plan?
we know that
The Unlimited Mileage plan for a Luxury car is $105 per day (see the table)
The trip are three days
so
To find the total cost multiply $105 by 3

Part c) Which is the better plan?
Compare

therefore
For this trip the better plan is the Standard Daily Rate plus Mileage plan