T(m) ---- the cost of a taxi ride as a function of the miles driven
T(m)=3+0.25m ---- $3 flat fee plus $0.25 per mile driven
$3 is added on as the y-intercept, or the initial fee. and 0.25 is the slope of the equation, given to you in the phrase "quantity per mile," per being the tip-off. this sentence also tells you that "miles" is our independent variable (basically our "x") because it comes after the "per."
