Solve Decimal Addition: 0.8 + 0.4 Step-by-Step

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

• Step 1: Align the numbers by their decimal points:
  $0.8$
  $+0.4$

• Step 2: Add each corresponding position from right to left:

Adding the tenths place, we have $8 + 4 = 12$. Write down the $2$ and carry over the $1$ to the ones place.

Add the ones place, which includes the carried-over $1$:
$0 + 0 + 1 = 1$.

Combining this, the sum of $0.8$ and $0.4$ is $1.2$.

Therefore, the solution to the problem is $1.2$. This corresponds to choice 2.