If the median is 18 what is the missing digit if the digits are 12 17 21 13 25 and a blank

So you have;
12, 13, 17, _, 21, 25

The mean of 17 and the missing number is 18.
Find out the missing number by multiplying 18 by 2, then subtract it by 17

18 x 2 = 36
36 - 17 = 19

The missing number is 19

Put the numbers in order
12,13,17,21,25,x

(17 + x) / 2 = 18
17 + x = 36
x = 36 - 17
x = 19

lets try it...
12,13,17,19,21,25now take the 2 middle numbers, add them, then divide by 2 to get the median
(17 + 19) / 2 = 18
36/2 = 18
18 = 18 (correct)

ur missing number is 19 <===