Linda has completed 24 deliveries so far this week. she needs to make 40 deliveries for the week. what percentage of her deliveries has linda completed?

Linda would have completed 100% after she makes 40 deliveries. That being said, 24 is part of that 100% percent but we don't know the answer yet, so we represent that unknown percentage with an "x"
Therefore, 40 = 100% and 24 = x%
Your equation then is:

That 60 is the 60% of completion. 

The first digit is in the middle school 100s place