What number comes next?
2,7,8,3,12,9

The first, third and fifth number are even numbers. 2, 8, 12

And the second, forth and sixth numbers are odd numbers. 7, 3, 9 

1. y = c + 2x

c1= 2 (and subsequent c= next number in the series) and x is in reducing order:

2 + 2x3 = 8

8 + 2x2 = 12

12 + 2x1 = 14 

2.  u = a (+-) 2(v).   

a1=7 (and subsequent a= next number in the series) and v is in increasing order.

7 - 2x2 = 3

3 + 2x3 = 9

9 - 2x4 = 1 

the subsequent number is an even number, so it should be 14

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step-by-step explanation: