Answer
When we are given the intercept and the slope of a line, we can substitute the slope for $m$ and plug in the y-intercept for $y_{1}$.
Also, since we know the y-intercept, we can substitute the $x_{1}$ for 0.
Work Step by Step
$y-y_{1} = m(x-x_{1})$
Example: slope is 3, y-intercept is 7
Thus, we know $m=3$ and $(0,7)$ is a point on the line.
$y-y_{1} = m(x-x_{1})$
$y-7 = 3(x-0)$
$y-7=3x-3*0$
$y-7=3x-0$
$y-7=3x$
$y=3x+7$
