Answer
$a.\quad 0.16$
$b.\quad $
$0.16, $
$ 0.16\%$ per minute of exercise
Work Step by Step
Use: $m=\displaystyle \frac{\text{change in y}}{\text{change in x}}=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$
$(a)$
The slope of the line passing through $(80,26)$ and $(180,42)$ is
$m=\displaystyle \frac{42-26}{180-80}=\frac{16}{100}=0.16$
$(b)$
The slope written as $\displaystyle \frac{\text{change in y}}{\text{change in x}}=\frac{0.16}{1}$
is interpreted as:
For a 1 minute change in x, remission of depression (y) increases by $ 0.16\%$.
The unit for slope is (unit for y)/(unit for x).
Here: "percent per minute of exercise"