For the ones that are struggling with the question: Two plumbing companies charge money for each hour of work, plus a one-time fee. A Plus Plumbing charges according to this table:
How much does A Plus Plumbing cost for each hour of work? How do you know?
The answer is: $60 per each hour of work, shown by the change in rate each hour after the one-time fee.
What is the one-time fee for A Plus Plumbing? How do you know?
$80 one time fee, found by determining the cost per hour by finding the rate of change. Then we subtract the cost per hour from $140.
How much does Quality Plumbing cost for each hour of work? How do you know?
$50 is the cost for each hour of work, which is determined by finding the slope of the line.
What is the one-time fee for Quality Plumbing? How do you know?
$150 is the one time fee, which is determined by finding the y-intercept.
Can A Plus Plumbing and Quality Plumbing ever charge the same total for the same amount of time? How do you know?
Yes, A Plus Plumbing has a lower one-time fee but costs more per hour, so it will eventually catch up to Quality Plumbing.