Your code does not compile. You need parentheses after function names for the declarations:
def AdiçãoDenominadoresIguais():
print(f"{Nfração1 + Nfração2} / {Dfração1}")
def SubtraçãoDenominadoresIguais():
print(f"{Nfração1 - Nfração2} / {Dfração1}")
After this fix, your code compiles. Also, it seems to work just fine for me. Can you provide inputs that don't seem to work for you for the code above (not any other version, I can only see the version you shared)?