We are given equations y =3.5x and y=25x +40.50.
Where x represent time in hours and y represents cost in dollars.
We need to determine that which equation is not the equation of a proportional relationship?
In first equation we have slope 3.5 and y-intercept 0.
In second equation, we have slope 25 and y-intercept 40.50.
In order to have a a proportional relationship, there should be y-intercept =0.
Therefore, y= 25x + 40.50 is not the equation of a proportional relationship.