How to average numbers generated by formulas?

[Peter h]

[TABLE="class: grid, width: 500"]
<tbody>[TR]
[TD]A
[/TD]
[TD]B
[/TD]
[TD]Formula in N
[/TD]
[TD]Result of formula
[/TD]
[/TR]
[TR]
[TD]05/28/2019 05:15
[/TD]
[TD]05/28/2019 05:00
[/TD]
[TD]=IF(A3="","",TEXT(TIMEVALUE(TEXT(A3,"HH:mm"))-TIMEVALUE(TEXT(B3,"HH:mm")),"hh:mm"))
[/TD]
[TD]00:15
[/TD]
[/TR]
</tbody>[/TABLE]


This has to be simple, and don't know why I'm unable to think of how to do this, but I need some help.

I've got dates and times in columns A and B, and a formula in N that calculates the difference of those 2 times. What I want is a formula that shows me the average difference in the last 20 rows. So, here's what my data looks like.

 

[Repush]

there must something you're not telling us . . because why is al this converting to text necessary?
N3: =A3-B3, copy down
N24: =AVERAGE(N3:N23)

 

[Peter h]

there must something you're not telling us . . because why is al this converting to text necessary?
N3: =A3-B3, copy down
N24: =AVERAGE(N3:N23)

The convertions to text is only because I'm an idiot that over complicates things... lol. I tried using A3-B3 and it returned 01/00/1900 00:24:02, and instead of realizing I could just change the format of the cell to hh:mm, I thought it was not reading the cells correctly. So I went the long way around extracting the hours and minutes as strings to get the desired results. Only when you answered my question did it dawn on me to just change the format of the cells. Thanks for enlightening me.

 

[Repush]

- I NEVER do that . . (not)
thanks for the feedback