I don't get this part can somebody help pls?

Find the slope of the line below . enter your answer as a fraction or decimal. use a slash mark ( / ) as the fraction bar if necessary

The function models the number of accidents

Your car's gasoline tank holds 18 gallons of gasoline. on a trip in canada, the tank is one-quarter full. you want to fill the tank. how many liters of gasoline are needed to fill the tank