out of my depth. Can anyone help?

Hello,

I struggle with math and have a problem. I'm making a spreadsheet for work so I can easily convert one figure to another. The thing is, the two columns of data I have (24 pairs of numbers) don't run parallel on a graph. I have some learning difficulties which irritatingly enough mean I can kind of see what I'm doing, but can't find the missing piece. grr! (Doh)

Can somebody please help before I lose my marbles?

The data is as follows:

1 = 3

2 = 5

3 = 7

4 = 9

5 =12

6=14

7=16

8=18

9=21

10=23

11=25

12=27

13=30

14=32

15=34

16=36

17=39

18=41

19=43

20=45

21=48

22=50

23=52

24=54

I had a conversion kind of figured out at 0.33 or 4.33 (i think) but it doesn't work for all the values. I have a GCSE/Highschool C and I haven't used it much in 15 years. I put it to the forum and cross my fingers.

Thanks,

Dave