THere is difference of 4,3,4,3,4,3....in sequences.. 8+4=12 12-3=9

9+4=13 13-3=10

10+4=14 14-3=11

11+4=15 15-3=12

Alternatively numbers are increased by 1 So 15&13

15,12 is the answer. Alternate number and step up by 1.

It follows the logic 8+4=12 12-3=9 9+4-13 13-3=10 10+4=14 14-3=11 11+4=15 15-3=12

answer is 15 and 12