How do you write the standard form of the equation given (3,-1) and slope -1?

Standard form: $y = m x + b$, where $m$ is the slope and $b$ is the y-intercept.
$y = - 1$ and $x = 3$ and $m = - 1$
In order to find $b$, plug in knowns, listed above.
$- 1 = - 3 + b$
To solve for $b$, move $- 3$ to the other side of the equation.
$- 1 + 3 = b$
$b = 2$
Standard form equation: $y = - x + 2$