12
31
38
20
It is 38, the middle number when they are arranged in order.
The next number is 20.
31
31.
12
The HCF of 38 and 40 is 2
38
31
38
In a series of numbers, there are rhythms that change. In the order of 100, 140, and 40, the number that would come next would be 80 because 40 should be added.
6
20
8, each number is a fifth of the last.