Number in sequence 3,-6,12,4,20

Number in sequence 3,-6,12,4,20 is expanded in the following way

Step-by-step explanation:

There are 2 series clubbed together

Odd place series 3 12 20 ?

Even place series -6 4 ?

These numbers are related in the following way, beginning with 3:

First, we subtract 9 to get -6

3 - 9 = -6

Next, we add 18

-6 + 18 = 12

To get from 12 to 4, we subtract 8:

12 - 8 = 4

and to get from 4 to the final number of 20, we must add 16

4 + 16 = 20

We need to examine the numbers that we add/take away in the sequence to find a pattern so we can predict the next number.

Even place numbers are getting subtracted starting from number 9 and it kept on decreasing for successive odd positions.

Odd place numbers are getting added with twice the number which has been previously subtracted..

hence next number will be

20–7 = 13..