Evaluate the expression when x = – 9.

x + ( – 3)

Rule: The sum of any integer and its opposite is equal to zero.

Explanation: Adding two positive integers always yields a positive sum; adding two negative integers always yields a negative sum. To find the sum of a positive and a negative integer, take the absolute value of each integer and then subtract these values.

To add two numbers with the same sign, first add the two numbers ignoring the sign and then put their common sign before the answer.

To add two numbers with the opposite sign, ignore their signs and subtract the smaller number from the bigger number. Then put the sign of the bigger number before the answer

To add two integers, we need the signs of those two integers.

Rule: If they are with same sign (both are positive or negative), then add the numbers and put their common sign (positive or negative) before the answer.

To find the value of the expression x + (– 3), substitute x = – 9

, so x+ (– 3) = – 12 when x = – 9