Apply sign rules for +/-/x/div on signed numbers without hesitation.
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Adding
Subtracting: change it to adding the opposite. \(15 - (-6) = 15 + 6 = 21\). \(3 - 11 = 3 + (-11) = -8\).
Multiplying and dividing: same signs give a positive, different signs give a negative. \(-4 \times (-12) = 48\) and \(8 \times (-6) = -48\). With many factors, count the negatives: an even count gives a positive answer.
Long strings: change every subtraction to adding, then combine. \(5 + (-2) - (-7) = 5 - 2 + 7 = 10\).
Common slips: reading \(-(-4)\) as \(-4\), and using the multiplication rule for addition (\(-3 + (-4)\) is \(-7\), not \(7\)).
Apply the sign rules while subtracting: \(-13 - (-10) = -3\). Getting the sign of the answer wrong gives \(3\). Adding instead of subtracting gives \(-23\). Ignoring the signs and adding the sizes gives \(23\).
Work left to right, tracking signs: \(14 - 1 = 13\), then \(13 - (-6) = 19\). Adding \(1\) instead of subtracting it gives \(21\). Adding \(-6\) instead of subtracting it gives \(7\). Getting the sign of the answer wrong gives \(-19\).
Apply the sign rules while multiplying: \(-6 \times (-19) = 114\). Getting the sign of the answer wrong gives \(-114\). Adding instead of multiplying gives \(-25\). Ignoring the signs and adding the sizes gives \(25\).