why 9 output of this code

Question

class wow:
def __init__(s, x):
s.x = x
def __add__(s, y):
return wow(s.x - y.x)
def __sub__(s, y):
return wow(s.x + y.x)
def __repr__(s):
return str(s.x)
a = wow(5)
b = wow(7)
c = wow(3)
print(a - b + c)

Answer 1

Because __sub__ is defined as addition (+) and __add__ as subtraction (-). As a result,

5-7+3

is evaluated as

5+7-3

which results in 9.

Answer 2

Thank you!