Question 1100053
<br>Without any instructions for what kind of sequence this is supposed to be, you can put any number next, and it will be a valid answer.<br>
With only three numbers given, you can always find a POSSIBLE answer by looking at the differences between the terms:
From 12 to 109 is an increase of 97.
From 109 to 210 is an increase of 101.
The amount of increase went up by 4; so MAYBE the next increase is 105, making the next number in the sequence 210+105 = 315.<br>
But that can only be considered as a guess....