What is the average of the numbers 37 76 92 96 81

You've got five (5) numbers to average.
First you add them together:
37+76+92+96+81=382
Then you divide that by the number of numbers you started with:
382 divided by 5 is 76.4.

Why does this work?
Imagine you had a stick 382" long and you wanted to divide it into 5 equal parts. Easy enough, you just divide the length by 5. But what if you didn't know the stick was 382" long? And what if you only had an 8' tape measure (96")?
One way is to measure off several lengths that are within the range of your tape measure and put a pencil mark at each length, then add up all the lengths.
So, if you put a pencil mark at 81" from one end of the stick, and then another pencil mark 76" from the first mark, then another pencil mark 92" from that mark, then another mark 96" from that mark, you'd find out that the last mark was only 37" from the other end of the really long stick.
So, you'd add all those measured lengths up to get the total length which is 382". But you don't want different lengths, you want equal (or average) lengths. So you divide the total length by 5.