If i work 8 hrs/day and it takes 30 minutes for me to resolved a customer svc issue - how many customers can i handle in an 8 hour day? i take two 15 min breaks and 30 minute lunch.

8 hours is the same as 480 minutes
The two 15 minute breaks add up to 30minutes
and then another 30 minutes for the lunch break
That makes a total of 60 minutes you are not working so subtract that from 480
480-60=420
Then you know each customer takes 30minutes to handle so do 420/30
420/30=14

You can handle 14 hours in an 8 hour day

|-5| + | 6| = 5 + 6 = 11