$\"\"$

The given values are $\"\"$ .

The sum of an arithmetic series $\"\"$ .

Where $\"\"$ is the first term and $\"\"$ is the nth term.

$\"\"$ (Substitute $\"\"$ )

$\"\"$ (Add: 43 + 115 = 158)

$\"\"$ (Multiply: $\"\"$ )

$\"\"$ (Divide: $\"\"$ $\"\"$ ) $\"\"$

The value of $\"\"$ .