Before ALL calculation, identify which operation it is!
Then follow the instructions for this operation.  
ADDITION

Have the numbers SAME SIGN?
YES - Same signs
Find the SUM:
  NO - Differnet signs:
Find theDIFFERENCE:
(-3) + (-6) = (-9)

(+4) + (+5) = (+9)
  (+5) + (-7) = (-2)

(-4) + (+6) = (+2)

Always:   Keep the sign of the number with the GREATER absolute value.
 
SUBSTRACTION

First, we must transform the SUBTRACTION into ADDITION;

Then we follow the rules for the ADDITION.

(-6) - (+2) =

1. The first number remains the same.

2. Turn subtraction into addition.

3. Invert the sign of the second number

4. Follow the rules for addition.

  

(-6) - (+2) =

(-6)

(-6) +

(-6) + (-2)

(-6) + (-2) = (-8)

Substract means:      
Add the opposit.

(+2) - (-6) =
(+2) + (+6) = (+8)

Substract means:      
Add the opposit.

(-7) - (-3) =
(-7) + (+3) = (-4)
Substract means:      
Add the opposit.

(+4) - (+9) =
(+4) + (-9) = (-5)
 
MULTIPLICATION OR DIVISION

First, YOU MUST DO the multiplication or division.

Then we determine the sign:

We count the number of negative signs....

Do we have a EVEN number of negative signs?
Yes AnEVEN number of négative sign the result is POSITIVE
NO AnODD number of négative sign the result is NEGATIVE
  (-2) * (-4) * (-6)

DO the multiplication or division, neglecting the signs:

  2 * 4 * 6 = 48

Count the number of negative signs ....
Determine the sign of the result: 		 

(-2) * (-4) * (-6) =

Is there an EVEN number of negative signs?
If YES , the result is POSITIVE
otherwise, the result is negative

  In total THREE NEGATIVE SIGNS
Three is ODD  .
So the result is NEGATIVE
-48


(4) ÷ (2) * (6) = 12
In total ZERO NEGATIVE SIGNS
ZERO IS EVEN .
So the result is POSITIVE


 
(4) ÷ (-2) * (6) = -12
In total ONE NEGATIVE SIGN
One is ODD .
So the result is NEGATIVE


 
(-4) ÷ (2) * (-6) = 12
In total TWO NEGATIVE SIGNS
TWO IS EVEN .
So the result is POSITIVE