Solve the Decimal Equation: Finding the Missing Value in ? + 2.4 = 4.5

Let's solve the problem step by step:

• Step 1: Identify the equation.
  The equation is $? + 2.4 = 4.5$.
• Step 2: Isolate the missing value.
  To find the missing number, subtract 2.4 from both sides.
• Step 3: Perform the subtraction.
  The calculation is $4.5 - 2.4$.
• Step 4: Calculate the difference.
  Start with the tenths place: $5 - 4 = 1$ in the tenths place.
  Subtract the whole numbers: $4 - 2 = 2$. Thus, the complete subtraction is $2.1$.

Therefore, the missing value that satisfies the equation $? + 2.4 = 4.5$ is $2.1$.