Solve the Decimal Equation: Finding the Missing Value in 4.5 - ? = 2.1

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

• Step 1: Identify the provided equation and rearrange it to solve for the missing number.
• Step 2: Substitute the known values to isolate the missing variable.
• Step 3: Perform the arithmetic operation to find the result.
• Step 4: Ensure the result matches one of the given choices, confirming its correctness.

Now, let's work through each step:
Step 1: The equation given is $4.5 - ? = 2.1$.
Step 2: Rearrange the equation to isolate the unknown:
We add '?' to both sides and subtract 2.1 from 4.5 to obtain:
$? = 4.5 - 2.1$.
Step 3: Perform the calculation:
$4.5 - 2.1 = 2.4$.
Step 4: Verify the answer by comparing it to the provided choices and checking the answer given:
The correct answer is indeed 2.4, which matches the given correct solution.

Therefore, the solution to the problem is $? = 2.4$.