Answer:
The new car travels 247.5 miles more than the old one on 30 gallons of gas.
Step-by-step explanation:
The fuel consumption of the old car was:
[tex]car_{old} = 18 + \frac{1}{4} = \frac{73}{4} \text{ miles per gallon}[/tex]
The new one can travel a distance of 390 7/8 miles by using 14 3/4 gallons of fuel, therefore the consumption is:
[tex]car_{new} = \frac{390.875}{14.75} = 26.5 \text{ miles per gallon}[/tex]
If the tank holds 30 gallons, on the old car the distance would be:
[tex]distance_{old} = 18.25*30 = 547.5 \text{ miles}[/tex]
On the new one it will be:
[tex]distance_{new} = 26.5*30 = 795 \text{ miles}[/tex]
So the new car is able to travel 247.5 miles more than the old one on 30 gallons of gas.