No.
Yes.
(0 + 12)/2 = 6 this is different from halfway between 1 & 12 because of starting the range at 0
42
If that's 0 and 12, halfway is 6/1 If that's 0 and 1/2, halfway is 1/4
19.5 is halfway between 18 and 21
There is no distance between them.
42
37
No.
21
Yes.
It is: (18+21)/2 = 19.5
Add 55 and 21, then divide by 2 = 38
(0 + 12)/2 = 6 this is different from halfway between 1 & 12 because of starting the range at 0
42
15