Arithmetic is in postfix notation, along with every other operator in O.
Numbers are the easiest objects to modify. Doing basic arithmetic is as easy as putting the sign you want.
Addition uses the + operator.
+
>>> 12+o 3
Subtraction uses the  operator.

>>> 75o 2
Multiplication uses the * operator.
*
>>> 85*o 40
Division uses the / operator.
/
>>> 42/o 2
Remainders will go out to 6 decimal places.
>>> 54/o 1.25 >>> 5/3 1.666667