median = the middle number {always remember this}.
To find the median of a set of numbers we arrange that set of numbers either in ascending order (smallest to biggest value) or in descending order ( biggest to smallest value).
so we are given :
20, 19, 13 , 23, 16, 15 , 17, 17, 15 , 15, 22, 19, .
we rearrange in ascending order (I chose ascending order).
Soo...
13, 15, 15, 15, 16, 17, 17 , 19, 19, 20, 22, 23.
so we cancel out (we cancel out left number, right number)
I mean
cancel out 13, cancel out 23
cancel out 15, cancel out 22
cancel out 15, cancel out 20 and so on.....
after that we will be left with 2 numbers which are 17 and 17.
NOTE: ( if we get 2 numbers instead of 1, then we add those 2 numbers and divide by 2)
so...
17 + 17 = 34
34/2 = 17.
the median of the set of numbers is equal to 17.
Hope this helps.
Good luck ✅.