Answer
$y_{1}$=12
Work Step by Step
It's given that slope=-2=m, and $x_{1}$=2, $x_{2}$=4, $y_{2}$=8, and we are trying to find $y_{1}$. Since m=$\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$, if we multiply by ($x_{2}$-$x_{1})$ on both sides, we get m($x_{2}$-$x_{1}$)=$y_{2}$-$y_{1}$. If we add $y_{1}$ to both sides and subtract m($x_{2}$-$x_{1})$ from both sides we get $y_{1}$=$y_{2}$-m($x_{2}$-$x_{1})$. Then we just plug in the givens, so $y_{1}$=(8)-(-2)(4-2)=8-(-4)=12
