Question

What is the next four numbers in the pattern below 20,15,10,5,

Answer 1

0,-5,-10,-15. It is that simple. All you had to do is keep counting down.
Hope this helps :)

Answer 2

5,10,15,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90,95,100,