The linear equation that represents how many more hours Kelley must work to afford the phone is 3x - 45 = 0
Functions are expressions represented in terms of a variable.
From the question, we have the following
Total number of hours = 45
If she works 3 hours per day and has worked x days, the total number of hours she needs to work is 3x
Equating to the total hours wwill give:
3x = 45
3x - 45 = 0
Hence the linear equation that represents how many more hours Kelley must work to afford the phone is 3x - 45 = 0
Learn more on linear equation here: https://brainly.com/question/14323743