18 X 2 – 6/3

Question

18 x 2 = 36

3 x -2 = -6

36 + -2 = -34

Is this correct?

Answer 1

18 x 2 = 36 (correct)

3 x (-2) = -6 (correct)

36 + (-2) = -34 (incorrect) ==> Note: can be re-written as 36 - 2 = 34.

12 - 15  = -3 ==> same as 12 + (-15) = -3

-45 - 5  = -50 ==> same as writing -45 + (-5) = -50

Adding two positives: Positive always (4 + 3 = 7)
Adding a positive and a negative: Momentarily ignore the signs. Subtract the smaller number from the larger and keep the sign of the larger. (3 - 4 = -1)
Adding two negatives: Sum the values and keep the sign negative (-3 - 4 = -7). Adding a negative value to an already negative number makes it more negative, so to speak.

Multiplication/Division

Mult/divide two positives: Always positive
Mult/divide a positive and a negative: Always negative
Mult/divide two negatives: Always positive

In fact, for mult/division, an even number of negative signs is always positive, while an odd number is always negative. 

(-3)x(-4)x(-2) = odd number of negatives = negative 24

(-3)x(-4)x(2) = even number of negatives = positive 24