Here you go, hope it helps:)
Assuming you want the slope, the answer is -2/-3.
X-change: -2
Y-change: -3
X-c/Y-c = -2/-3
If -2/-3 is not an answer, try 2/3 or .666 (infinite 6s).
Okay so on average if they can go 25 miles per gallon that would mean you could just multiply 25 and 7 to get 175. So on average they could go 175 miles on 7 gallons of gas. Keep in mind that the answer can and will change depending on traffic, how fast or slow they are going, and if they are traveling behind a big-rig that moves more air that would normally be putting pressure on the car to push out of the way but the big-rig helps save gas but it can also waste more gas if they are driving slower then normal.
Sorry for the extra information once I start it's hard to stop. Any way I hope this helps.
893.76/0.21=4256
Hope this helps and have a nice day/night!!!