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**stevembe** Sorry if I sound a bit dim but I am in a bit of a panic as I have a son worried about his homework which is due in tomorrow. He has a sheet with two rows and five columns as follows:

Position 1 2 3 4

Term 9 13 17 21

The first question is:

a. What is the term to term rule? (how do you get from 9 to 13, 13 to 17?)

I have worked this out as the term rule is term + 4.

The next bit has thrown me:

b. What is the position to term rule? (how do you get from 1 to 9, 2 to 13?)

The position to term rule is (position number x ......)

Completely lost, can anybody help and advise on how I can explain this to my son?

Many thanks in advance.