I dont understand this quiz question

Question

I don't know how you would get his answer

https://code.sololearn.com/c7qP2uh7y5wh/?ref=app

Answer 1

Recursion.

def kys (x):
if x == 0:
return 0
else:
return kys(x-1)+100

# i.e. :
# kys(3)
# when expanded, is
# -> kys(3-1) + 100
# -> kys(2-1) + 100 + 100
# -> kys(1-1) + 100 + 100 + 100
# -> 0 + 100 + 100 + 100
# -> 300

Answer 2

Exactly as reflected in my answer.

kys(1-1) returns 0

Answer 3

oh I understand now it returns 0 which the 100s get added to it

Answer 4

but when x = 0 wouldn't it just return 0