Answer
$8$ feet
Work Step by Step
First, find the growth rate of the tree from the graph. For growth rate, determine the slope of the graph. Using points on the graph $(0,4)$ and $(4,6)$ and putting them into point slope formula, we find slope like this:
$$\frac{6-4}{4-0}=\frac{2}{4}=\frac{1}{2}.$$
Now using $y=mx+b$, $m$ is slope/growth rate, so $m=\frac{1}{2}$.
Since we are being asked about the hypothetical situation of the tree being $5$ feet when planted (at $0$ years), we set $b$ equal to $5$. We want to know the height of the tree at $6$ years, or when $x=6$. Plugging all the variables into $y=mx+b$ gives the equation
$$y = \frac{1}{2}(6) + 5.$$
Solve to get the final answer like this:
$y = \frac{1}{2}(6) + 5$
$y = 3 + 5$
$y = 8$
