Answer
slope m, ..., 3
Work Step by Step
Slope of the line $y=mx+b$ is defined as
$m=\displaystyle \frac{\Delta y}{\Delta x} =\displaystyle \frac{Rise}{Run}$,
If x increases by k units,
y will increase by 3k units (as given by the text).
So, $\displaystyle \quad m=\frac{3k}{k}=k$
The slope is $m=3$
