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
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.