$\"\"$

\

The given values $\"\"$ .

\

Where $\"\"$ is first term of the sequence and d is common difference.

\

The nth term of an arithmetic sequence is $\"\"$ .

\

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

\

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

\

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

\

Apply addition property of equality: a = b then a + c = b + c.

\

$\"\"$ (Add 60 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: $\"\"$ )

\

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

\

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

\

The value of $\"\"$ .