Calculate the Sum: 10.04 + 3.08 Decimal Addition

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

• Step 1: Align the numbers by their decimal points.

• Step 2: Add the digits column by column, starting from the rightmost column.

• Step 3: Place the decimal point in the result directly under the other decimal points.

Now, let's work through each step:
Step 1: Align the numbers: $\begin{array}{c} ~10.04 \\ + \, 3.08 \\ \hline \end{array}$
Step 2: Add each column, starting from the right:
- Add the hundredths place: $4 + 8 = 12$. Write down 2, carry over 1.
- Add the tenths place: $0 + 0 = 0$. Add the carried over 1 to get 1.
- Add the units place: $0 + 3 = 3$.
- Add the tens place: $1 + 0 = 1$. Place the decimal point directly below the other decimals:
$\begin{array}{c} ~~10.04 \\ + \ 3.08 \\ \hline ~~13.12 \\ \end{array}$

Therefore, the correct answer to $10.04 + 3.08$ is $13.12$.