Sam is observing the velocity of a car at different times. after three hours, the velocity of the car is 53 km/h. after six hours, the velocity of the car is 62 km/h.
part a: write an equation in two variables in the standard form that can be used to describe the velocity of the car at different times. show your work and define the variables used.

part b: how can you graph the equation obtained in part a for the first seven hours?

For the answer to the question above, first find out the gradient. 

m = rise/run 
=(y2-y1)/(x2-x1) 

the x's and y's are the points given: "After three hours, the velocity of the car is 53 km/h. After six hours, the velocity of the car is 62 km/h" 
(x1,y1) = (3,53) 
(x2,y2) = (6,62) 

sub values back into the equation 
m = (62-53)/(6-3) 
m = 9/3 
m = 3 

now we use a point-slope form to find the the standard form 
y-y1 = m(x-x1) 
where x1 and y1 are any set of point given 
y-53 = 3(x-3) 
y-53 = 3x - 9 
y = 3x - 9 + 53 
y = 3x + 44 

y is the velocity of the car, x is the time.
I hope this helps.

26.4 is about the right time