Complete the Number Sequence: Finding Missing Terms in 25, 21, 19, ...

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

• Step 1: Determine the common difference by looking at the known terms, 21 and 19.
• Step 2: Apply the common difference to find the missing terms in the sequence.
• Step 3: Verify the sequence pattern to ensure accuracy.

Now, let's work through each step:

Step 1: The common difference between 21 and 19 is 2. Thus, each number in the sequence is reduced by 2 from the previous one.

Step 2: Starting from 25, subtract 2 to fill in the first gap: $25 - 2 = 23$. Now the sequence is 25, 23, ..., 21, 19.

From 19, subtract 2 to fill in the next gap: $19 - 2 = 17$, then $17 - 2 = 15$. Thus, the complete sequence is:

$25, 23, 21, 19, 17, 15$

Therefore, the solution to the problem is $25, 23, 21, 19, 17, 15$.