Identify the Predecessor of 6900 in Sequence Exploration

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

• Identify the number given as the "next" one, which is 6900.
• Use the concept of consecutive numbers to find the predecessor of 6900.

Now, let's work through the solution:
The problem states that the number after the unknown number is 6900. This means we are looking to find the number just before 6900, which is its predecessor.
To find the predecessor, subtract 1 from 6900:

$6900 - 1 = 6899$

Therefore, the solution to the problem is $6899$.