Place a pencil on the number line on the point indicated by the first integer in the problem. For instance, consider the problem 5 + 4. Put your pencil on the mark at the 5.
Move your pencil the number of tick marks to the right according to the value of the second integer. In the example of 5 + 4, count four tick marks to the right. Your pencil should land on the 9.
Write this number down; it is the solution. In this case, the answer is 9. Answers to problems involving the addition of two positive integers will always be positive.
Place your pencil on the spot on the number line indicated by the first integer. For example, in -3 + 8, put your pencil on the -3.
Move your pencil the number of spaces to the right that the second integer dictates. In -3 + 8, your pencil will land on 5.
Write down this number, which is your answer. In this case it is 5. Answers to this type of problem may be either positive or negative depending on the absolute values of the integers involved.
Place your pencil on the point on the number line specified by the first integer. In 2 + -9, your pencil should be on top of the 2.
Move your pencil the number of tick marks left equal to the absolute value of the second integer. Simply put, ignore the minus sign and move your pencil the indicated number of spaces to the left. In 2 + -9, move your pencil nine spaces left, landing on -7.
Write down the answer, which is the integer that your pencil landed on: -7 in this example. The answer may be positive or negative depending on the particular problem.
Place your pencil on the spot on the number line that the first integer indicates. Consider -1 + -7. Your pencil should be on the -1.
Move your pencil the number of spaces left equal to the second integer's absolute value. In the previous problem, move seven spaces to the left, ending at -8.
Make note of this number, which is your solution: -8 in this case. When adding two negative integers, your answer will always be negative.