SOLUTION: I have a question. I have been given to find the 15th term, when I know the 3rd term to be 7 and 20th term to 43. I trying to figure the common difference and the what the 15th ter

Question 308365: I have a question. I have been given to find the 15th term, when I know the 3rd term to be 7 and 20th term to 43. I trying to figure the common difference and the what the 15th term is.
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!

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So now you have two equations with two unknowns.

You can re-arrange both of them,

Since they both equal , set them equal to each other and solve for .

Then use either equation to solve for .

Then the 15th term would be,

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