Answer:
9
Step-by-step explanation:
median: The middle number after the numbers have been sorted into ascending or descending order.
Mean: The quotient of the numbers added together then divided by the amount of numbers.
So if 9 were the missing number the median would be 5 because in ascending order it would look like this:
1, 3, 5, 7, 9
and as you can see 5 is in the middle.
The mean would also be 5 because
1+ 3+ 5 + 7 +9 =25
and 25 divided by 5 equals 5
So therefore the missing number must be 9.
(Also it was obvious that they just added 2 to each number)