Question 1047415
Rate is {{{(25/1)(miles/gallon)}}}  or {{{(1/25)(gallons/miles)}}}.


G, amount of fuel in gallons, in the tank.
Initial data point, ordered pair as (D,G), would be (0,18).
You want an expression to calculate G gallons of gasoline (or fuel), so pick the slope  {{{(1/25)(gallons/miles)}}}.  The data point identified is an axis intercept, on the vertical axis  (meaning on the G axis).


{{{highlight(G=-(1/25)D+18)}}}
The slope is really negative because the car is consuming amount of fuel, not gaining amount of fuel.