PEMDAS
Order in which to carry out a calculation
You first do...
Parentheses, then...
Exponents, then...
Multiplication, then...
Division, then...
Addition, and finally...
Subtraction
Beware, however, that multiplication and division are of the same order, as well as addition and subtraction. Within a term only involving multiplication and division you simply work from left to right. Example: 40 : 2 * 5 correctly yields 100 (and not 4). PEMDAS is often used in the United States.
See also:
=> Punkt vor Strich