Find the First Term a_n=-12+(n-1)*3

$a_{n} = - 12 + (n - 1) \cdot 3$

Substitute in the value of $n$ to find the $n$ th term.

$a_{1} = - 12 + ((1) - 1) \cdot 3$

Simplify each term.

Subtract $1$ from $1$ .

$a_{1} = - 12 + 0 \cdot 3$

Multiply $0$ by $3$ .

$a_{1} = - 12 + 0$

Add $- 12$ and $0$ .

$a_{1} = - 12$