Solve Vertical Addition: 21 + 59 Step-by-Step

To solve this problem, we will perform the following steps:

• Step 1: Align the given numbers vertically according to their place values.
• Step 2: Add the digits in the ones and tens places, carrying over if necessary.

Let's break down the calculation process:

Step 1: Write the numbers in a vertical format.
$\begin{aligned} &\phantom{0}21 \\ +&\phantom{0}59 \\ &\underline{\phantom{776}} \end{aligned}$

Step 2: Start by adding the ones digits: $1 + 9 = 10$. Since 10 is a two-digit number, we write 0 in the ones place and carry 1 over to the tens place.

Step 3: Now, add the tens digits, including the carried 1: $2 + 5 + 1 = 8$.

Since there is no further place value beyond tens in this problem, the result of the addition is:

$\begin{aligned} &\phantom{0}21 \\ +&\phantom{0}59 \\ &\underline{\phantom{8}80} \end{aligned}$

Therefore, the solution to the problem is 80.