Basic Mathematical Operations for Use in Statistics
The four basic mathematical operations are addition, subtraction, multiplication, and division (ah, yes — the basics you learned in elementary school). Different symbols indicate these operations.
Addition and subtraction
Addition and subtraction are always indicated by the + and – symbols, respectively, placed between two numbers or variables. The minus sign has some other tricks up its sleeve, though:

A minus sign immediately in front of a number means a negative quantity. For example, –5 could indicate five degrees below 0 or a weight loss of 5 kilograms.

A minus sign in front of a variable tells you to reverse the sign of the value of the variable. Therefore, –x means that if x is positive, you should now make it negative; but if x is negative, make it positive. Used this way, the minus sign is referred to as a unary operator, because it’s acting on only one variable.
Multiplication
Multiplication is indicated in several ways.
What It Is  Example  Where It’s Used 

Asterisk  2 * 5 = 10  Plain text formulas, but almost never in typeset formulas 
Cross  2 × 5 = 10  Typeset formula, between two variables or two constants being multiplied together 
Raised dot  2 · 5 = 10  Typeset formula 
Something immediately in front of a parenthesized expression 
2(5 + 3) = 16  Typeset formula 
Brackets and curly braces  2[6 + (5 + 3)/2] = 20  Typeset formula containing “nested” parentheses 
Two or more terms running together  2πr (versus 2 x π x r)  In typeset formulas only. 
You can’t run terms together to imply multiplication just anytime. For example, you can’t replace 5 x 3 with 53 because 53 is an actual number itself. And you shouldn’t replace length x width with lengthwidth because people may think you’re referring to a single variable named lengthwidth.
You may run terms together to imply multiplication only when it’s perfectly clear from the context of the formula that the authors are using only singleletter variable names and that they’re describing calculations where it makes sense to multiply those variables together, such as Area of a rectangle = hw, where h= height and w = width.
Division
Like multiplication, division is indicated in several ways:

A slash (/) in plain text formulas: Rate = Distance / Time

A division symbol in typeset formulas: Rate = Distance ÷ Time

A long horizontal bar in typeset formulas: