1. Multiplying Signed Numbers
When multiplying two numbers that are positive, you will get an answer that is positive.
When multiplying two numbers that have different signs, you will get an answer that is negative.
(+3) • (+ 12)
which is the same as
3 • 12 36
(+3) • (-12)
which is the same as
3 • -12
-36

2. Dividing Signed Numbers
The same rules apply when dividing signed numbers.
When dividing two numbers that are positive, you will get an answer that is positive.
When dividing two numbers that have different signs, you will get an answer that is negative.
24 ÷ 3 = 8
-24 ÷ 3 = -8

3. Multiplying Series of Numbers
Add the number of negative signs. If the total number is an even number, then your answer will be positive. If the total number is an odd number, then your answer will be negative.
(3)(-5)(-2)(-1)(-2)
Number of negative signs: 4
Answer will be positive. 60
(3)(5)(-2)(-1)(-2)
Number of negative signs: 3
Answer will be negative.
-60

4. Give it a try… 51
-504
-240
360

5. Learn them once; use them forever…
These sign rules will never change. It does not matter what type of problem you are working on.
Whole numbers, decimals, fractions, order of operations…the rules will never change!