pa help po please po ASAP po please po ASAP po please po

Step-by-step explanation:
15. 10,15,20,25,30,35,40
RULE:__I DONT KNOW SORRY_________
15. 30,35,40
16. 4,0,-4
17. 11,13,15
18. 14,17,20
19. 1/6,1/7,1/8