Find the Ones Digit: Identifying the Last Number in 89

To solve this problem, we'll follow these steps:

• Identify the place value of each digit in the number 89.
• The tens digit is the second rightmost digit, and the ones digit is the rightmost digit.
• Conclude by identifying the rightmost digit as the ones digit.

Now, let's work through each step:
Step 1: We examine the number 89 and recognize it has two digits: 8 and 9.
Step 2: In the decimal system, the digit in the rightmost position of any whole number represents the ones digit. Therefore, the ones digit in the number 89 is the digit 9.
Step 3: Thus, we can conclude that the ones digit of 89 is $9$.

Therefore, the solution to the problem is $9$.