Since the slope of a line is [tex] \frac{y_{2}-y_{1} }{ x_{2}-x_{1} } [/tex]
And 2 points of the line are given, (4,5) and (8,y) we can substitute those values into our equation.
[tex] \frac{y-5}{8-4} = \frac{y-5}{4} [/tex]
Since the slope of the line is 3,
[tex] \frac{y-5}{4} = 3[/tex]
Multiplying both sides by 4 would give us:
y-5=12
y=17
Therefore the missing y value equals 17.
