Find the value of the following.
`l x+my +nz` when x = 5, y = 7, z = 9 and l = m = n = 1

Answer

To find the value of the expression \( lx + my + nz \) when \( x = 5 \), \( y = 7 \), \( z = 9 \), and \( l = m = n = 1 \), we can follow these steps:

### Step 1: Write down the expression
The expression we need to evaluate is:
\[ lx + my + nz \]

### Step 2: Substitute the values
We know:
- \( x = 5 \)
- \( y = 7 \)
- \( z = 9 \)
- \( l = 1 \)
- \( m = 1 \)
- \( n = 1 \)

Now, substitute these values into the expression:
\[ 1 \cdot 5 + 1 \cdot 7 + 1 \cdot 9 \]

### Step 3: Simplify the expression
Now, we can simplify the expression:
\[ 5 + 7 + 9 \]

### Step 4: Perform the addition
Now, we add the numbers together:
\[ 5 + 7 = 12 \]
\[ 12 + 9 = 21 \]

### Final Answer
Thus, the value of the expression \( lx + my + nz \) is:
\[ \boxed{21} \]

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