23, 30, 1, 49, 2, 36, 7, 23, 13, 9, 30, 17, 20.

[The median is the middle number.]

Arrange them in ascending order:

1, 2, 7, 9, 13, 17, 20, 23, 23, 30, 30, 36, 49

Count these numbers.  There are 13 numbers.  That is an odd 
number.  Divide by 2. Get 6.5. round up to the next higher number.
Get 7.  Write down the 7th number in the list in ascending
order. Get 20.  That's the median.

[The mode is the number used most.]

There is no one number that is used most because 23 and 30 are both
used twice, which is more than any of the other numbers, so we say
"There is no mode, the list is bimodal".

Edwin