Answer:

Slope = 
Step-by-step explanation:
Let the equation representing the number of gallons left in the gas tank is,
G = mt + b
Where m = slope of the line
b = y-intercept of the line
Slope of the line passing through two points  and
 and  is,
 is,
'm' = 
Slope of the line passing through (8, 5) and (4, 10),
m = 
m = -
Equation of line will be,
G = 
Since, point (8, 5) lies on this line,
5 = 
5 = -10 + b
b = 15
Therefore equation of the function will be,
G = 
Here slope of the function represents the  gallons of gas is consumed to drive the car for one hour.
 gallons of gas is consumed to drive the car for one hour.