Question 1183971
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The message in the response from the other tutor is that any next number will form a valid sequence, so "?" can be any number.<br>
The general answer to ANY question like this is that there is no way to know what the "correct" answer is.<br>
So questions like this must be considered as recreational puzzles -- not as formal math problems.<br>
Take as much, or as little, time as you want looking for a relatively simple pattern that will generate the given sequence of numbers.<br>
One strategy that often works is to view the given sequence as two (or more) spliced sequences.  Using that strategy on this example gives a big hint as to what the expected answer is.<br><pre>
Given sequence...

   1  3  5  7 13 12 25 18 __

Separated into two separate sequences...

   1     5    13    25    __
      3     7    12    18</pre><br>
Look for similar patterns in those two sequences to determine the logical next number in the first sequence....<br>