(–71) + (+9) _______ (–81) + (–9)

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LHS:

To add a positive integer and a negative integer, we ignore the signs and subtract integer with smaller numerical value from the integer with larger numerical value and take the sign of the larger one.

Since 71 is the larger of the two numbers, negative sign is retained.

RHS:

To add negative integers, we add the corresponding positive integers and retain the negative sign with the sum.