Find the median of the data.
a.
25
b.
27
c.
27.5
d.
30

Both A.25 and D.30 are the median

1.First you need to put the numbers in order

15,15,20,25,25,30,30,35,45

2.You then need to cross one off each side as you go down (As below)

15,20,25,25,30,35
20,25,25,30
25,30

3.After you take all the numbers off you stop when there are no numbers to take off from both ends 

25,30

4.You are then left with these two median numbers so your answer is 25 and 30

I hope this explains it for you if you need any other information then please ask i wouldn't mind helping