[tex]y = 55x + 35[/tex]
35 being the y - intercept
55 being the slope
y being the total cost
~~
For a week??
[tex]y = 55(7) + 35[/tex]
Since there is 7 days in a week we will substitute the 7 for x.
[tex]y = 420[/tex]
~~
I hope that helps you out!!
Any more questions, please feel free to ask me and I will gladly help you out!!
~Zoey