How many hours is this ?

Working time in the first day
= (12 h + 5 h 20 min) - 8 h - 30 min
= 17 h 20 min - 8 h 30 min
= 16 h 80 min - 8 h 30 min
= 8 h 50 min

Working time in the other day
= (12 h + 4 h) - 8 h
= 8 h

Total working time
= 8 h 50 min + 8 h
= 16 h 50 min

= (16 and 5/6) h

First day: 8 am to 5:20 pm = 9 hrs. 20 mins. - 30 mins. = 8 hrs. 50 mins.
Second day:8 am to 4 pm = 8 hrs.
Total hrs. in the two days: 8 hrs. 50 mins. + 8 hrs. = 16 hrs. 50 mins.
Answer: 16 hrs. 50 mins.

 8 h 50 min + 8 h = 16 h 50 min

16 hours and 50 minutes 

"I worked from 8:00am had a 30 minute lunch and clocked out at 5:20."

For this the time is 17.20 - 8 = 9 hours 20 minutes (under 24 hours format)
 9 hours 20 minutes - 30 minutes lunch break = 8 hours 50 minutes.

"Then the other day I worked from 8am to 4pm"

For this the time is 16 - 8 = 8 hours (under 24 hours format)

Day 1,  8 hour 50 minutes
Day 2,  8 hours                  +

Total     16 hours 50 minutes.

(17.333 - 8 - 0.5) + (16 - 8) = 16.8333 = 16 hours 50 minutes

5:20pm = 17.333
8am = 8
4pm = 16
30 minutes = 0.5

I worked from 8:00 am had a 30 minute lunch and clocked out at 5:20. 
Then the other day I worked from 8 am to 4 pm.
8 h 50 m + 8 h = 16 h 50 m