Data:
Enrollment: $79
Charge per Month: $45/month
x: number of months
y: Total cost
You can follow the next general expression:
[tex]y=kx+b[/tex]Where k is the constant of change, in this case the charge per month, and b is the charge at time 0, in this case the charge per enrollment.
Then, You get the next expression that represents the relationship:[tex]y=45x+79[/tex]