Median is the middle number of the list so write the numbers in ascending or descending order in 1,4,9,15,17,18 : This is even list so add 9 and 15 and then divide the answer by 2

median = (9+15)/2

= 24/2

=12

median = 12 >>answer

median = (9+15)/2

= 24/2

=12

median = 12 >>answer