Draw a number line. Label the middle of the line "0." Label numbers to the right of the zero as positive integers, starting with "+1." Label the numbers to the left of the "0" as negative integers, starting with "-1." Use the number line as your reference for solving integer subtraction problems.
Look at the integer subtraction problem. Switch the subtraction symbol (-) to an addition symbol (+) to follow the rule of "adding the opposite" when subtracting integers.
Change the symbol in front of the second integer into the opposite. For example, switch a positive (+) symbol to a negative (-) symbol, and a negative (-) symbol to a positive (+) symbol. Note that the second integer is initially considered positive if it does not have a symbol in front of it and must be switched to a negative.
Rewrite the integer subtraction problem to turn it into an addition problem. For instance, if the original problem was (8) - (-5), rewrite it as (8) + (+5) to reach the solution of +13. This follows the rule of "adding the opposite."
Solve the problem to find the difference. Adding two negatives results in a negative integer versus adding two positives, which results in a positive integer. If adding a negative and positive, your answer will be negative if the negative number is larger than the positive; or it will be positive, if the positive integer is the highest amount. For example, in the problem (-10) + (5) = -5, the 10 negatives outweigh the 5 positives, so the answer must be negative.
Check your integer subtraction solution using the number line. Place your finger on the first integer indicated in the problem. Look at the second integer in the problem. If the second integer is negative, move your finger to the left on the number line by the amount of the second integer. If the second integer is positive, move your finger to the right on the number line by the amount of the second integer.