The letter n corresponds with the number of the term, so the first term would be 25 - 3(1). The second would be 25 - 3(2) and so on. To find the number term you could plug in each number until you found your answer, so plug in 3, then 4, then 5 etc.

Another way is to consider how many times 3 goes into 25. We know its a little more than 8 as 3x8=24 so we can try the next number, 9. If we plug in... more