There is no distance between them.
The number halfway between 18 and 21 can be found by taking the average of the two numbers. To do this, add 18 and 21 together to get 39, then divide by 2 to get 19.5. Therefore, the number halfway between 18 and 21 is 19.5.
42
37
The number halfway between 13 and 21 can be found by taking the average of the two numbers. Add 13 and 21 together to get 34, then divide by 2 to get 17. Therefore, the number halfway between 13 and 21 is 17.
21
Yes.
It is: (18+21)/2 = 19.5
Add 55 and 21, then divide by 2 = 38
42
The answer is 1414
(21+29)/2 = 50/2 = 25
(21 + 69)/2 = 90/2 = 45