Answer
y=14 inches
Work Step by Step
We are given that the equation is $y=2x+6$, where y is the perimeter of a rectangle whose width is a constant 3 inches and whose length is x inches.
We can plug in $x=4$ into the equation to calculate the perimeter.
$y=2\times4+6=8+6=14$ inches
This y-coordinate corresponds to x=4 on the graph of the equation.