$\"\"$

\

The given values are $\"\"$ .

\

The nth term of the arithmetic series $\"\"$ .

\

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

\

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

\

$\"\"$ (Subtract: $\"\"$ )

\

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

\

Apply addition property of equality: a = b then $\"\"$ .

\

$\"\"$ (Add $\"\"$ to each side)

\

$\"\"$ (Apply additive inverse property: $\"\"$ )

\

$\"\"$ (Apply additive identity property: $\"\"$ )

\

$\"\"$ (Add: $\"\"$ ) $\"\"$

\

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

\

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

\

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

\

$\"\"$ (Subtract: $\"\"$ ) $\"\"$

\

The value of $\"\"$ .