Answer
$(a)$ See the image below.
$(b)$ $y = 6.45102x - 0.15228$
Where $y$ is age of the tree and $x$ is a diameter.
$(c)$ $116$ years
Work Step by Step
$(a)$ See the image above.
$(b)$ We can simply input the data into the regression line calculator and find the function:
$y = 6.45102x - 0.15228$
Where $y$ is age of the tree and $x$ is diameter.
$(c)$ If $x=18$
$y= 6.45102\times18 - 0.15228\approx 116$
