Question 1118234
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I always encourage students to try working problems informally if at all possible.  If you can do that, solving the problem by formal mathematical methods will make more sense.<br>
Let's do a little mental arithmetic here to find the answer.<br>
From the 4th term to the 22nd term is 18 terms; the difference between the 4th term and 22nd term is 1.  So the common difference between terms has to be 1/18.<br>
The 19th term is 3 terms before the 22nd term, which is 5: 5 - 3(1/18) = 5 - 3/18 = 5 - 1/6 = 4 5/6 or 29/6.