Switch 2 variable without using temp variable

Question

It is basic knowledge of algoritm, how to switch the value of 2 integer variable.
for example :
a = 9
b = 3

switch the value of this two variable so the result is :
a = 3
b = 9

without using the third (as temp) variable.

Answer 1

java,c++,javascript

a=a+b;
b=a-b;
a=a-b;

Answer 2

In Python: a, b = b, a :)

Answer 3

>>> a = 3
>>> b = 9
>>> a, b = b, a
>>> print (a)
9
>>> print(b)
3
>>>

Answer 4

c++

a=a+b;
b=a-b;
a=a-b;