Solve for the Missing Number: ? + 3.3 = 6.7

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

• Step 1: Understand the equation $? + 3.3 = 6.7$.
• Step 2: Rewrite the equation to solve for the missing value as $? = 6.7 - 3.3$.
• Step 3: Perform the subtraction to find the value of ?.

Begin by setting up the equation:
$\, ? + 3.3 = 6.7$
To solve for $?$, we rearrange the equation: $? = 6.7 - 3.3$

Perform the subtraction:
$6.7 - 3.3 = 3.4$

Thus, the missing value is 3.4. Hence, $? = 3.4$.

Therefore, the correct choice from the given options is choice 4: 3.4, which matches our calculated result.