Find three numbers that you want to determine are integers. For example, determine whether the numbers 1.2, -5 and 0 are integers.
Determine whether the first number contains a fraction or decimal, or whether it is 0. For example, the number 1.2 contains a decimal portion, 0.2. Therefore, the number is not an integer.
Determine whether the second number contains a fraction or decimal, or whether it is 0. For example, the number -5 contains no fraction or decimal. Therefore, by definition, the number -5 is an integer.
Determine whether the third number contains a fraction or decimal, or whether it is 0. For example, the third number is 0. By definition, this makes it an integer.