Thank you for the opportunity to help you with your question!

Thank you for the opportunity to help you with your question!

Let the number of days be x

Then the cost of hired the car for x days is given by $(55 +
8.5x)

In order to calculate the number of days whose of total cost
is 123,

Then we have the equation 55+8.5x = 123

Implying that 8.5x=123-55

8.5x=68

X=8

Thus the number of days is 8 days.

Please let me know if you need any clarification. I'm always happy to answer your questions.Please let me know if you need any clarification. I'm always happy to answer your questions.