M = Undefined (because the line is perfectly vertical)
Answer:
b = 
Step-by-step explanation:
divide both sides by a
OR
bring the a over to the other side and put it under the c as the opposite of times is divide
Y=5+4x
Because it is 5 dollars when you enter and then 4 dollars per round
1. Note that

2. Then the equation
can be rewritten

3. Solve it:

Answer: x=6