Answer
Blanks:$\quad$ dollar, miles
Work Step by Step
Slope of $y=mx+b$ is defined as
$m=\displaystyle \frac{\Delta y}{\Delta x} =\displaystyle \frac{Rise}{Run}$.
The slope m is measured in (units of y) per (unit of x).
x is the independent variable, and y (a function of x) is the dependent.
Given miles per dollar,
unit of x, the independent variable, is "dollar",
unit of y, the dependent variable, is "miles",
