Solve Three-Digit Addition: 367 + 421 in Vertical Format

$\begin{aligned} &367 \\ +& \\ &421 \\ &\underline{\phantom{776}} & \\ \end{aligned}$

To solve this addition problem, we will apply vertical addition:

We start with the given problem:

$\begin{aligned} &367 \\ +& \\ &421 \\ \end{aligned}$

We perform the addition column by column:

• Units Column: $7 + 1 = 8$
• Tens Column: $6 + 2 = 8$
• Hundreds Column: $3 + 4 = 7$

Putting it all together, the sum of the two numbers is:

$\begin{aligned} &788 \end{aligned}$

Therefore, the solution to the problem is $788$.