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Answer:
-1 + 2 = 1
1 + (-2) = -1
-1 - 2 = -3
1 - (-2) = 3
Step-by-step explanation
When you subtract use keep change change
Rule 1 when you add : If the signs are the same add the numbers and take the sign of the bigger number.
Rule 2 when you add : If the signs are different subtract the numbers and take the sign of the bigger number.
I wanted to help you understand and i hope i did that!