Add: `57+21+9`

Answer

To solve the problem of adding `57 + 21 + 9`, we can follow these steps:

### Step 1: Add the smaller numbers first
Let's start by adding the two smaller numbers, which are `21` and `9`.

\[ 21 + 9 = 30 \]

### Step 2: Rewrite the expression
Now, we can rewrite the original expression by replacing `21 + 9` with `30`. So, we have:

\[ 57 + 30 \]

### Step 3: Add the remaining numbers
Now, we will add `57` and `30`.

\[ 57 + 30 \]

To do this, we can add the units place first:

- The units place: \(7 + 0 = 7\)
- The tens place: \(5 + 3 = 8\)

So, combining these, we get:

\[ 57 + 30 = 87 \]

### Final Answer
Thus, the final answer is:

\[ \boxed{87} \]