You have to cast them as ints:
legs = int(raw_input("How many legs do you have? "))
arms = int(raw_input("And how many arms do you have? "))
Example
>>> number_of_limbs(legs, arms, limbs)
You have 2 legs O.o
You also have 2 arms o.O
You have 4 limbs!! O.O
This is because you are adding strings
and when you do string+string
it simply concatenates the two strings together. This is because the default type of raw_input
is str
>>> '2'+'2'
'22'
>>> int('2')+int('2')
4