Word problem for college algebra

Question

Scott is driving to Memphis. Suppose that the distance to his destination (in miles) is a linear function of his total driving time (in minutes). Scott has 64

 miles to his destination after 15

 minutes of driving, and he has 43.6

 miles to his destination after 39

 minutes of driving. How many miles will he have to his destination after 47

 minutes of driving?

Answer 1

(15, 64), (39, 43.6) are 2 points on a downward sloping line with slope =

-20.4/14

=-10.2/7=(y-64)/(x-15)

when x=47

=(y-64)/(47-15)

= (y-64)/32= -10.2/7

y-64=-32(10.2)/7

y= -326.4/7+64= -46 22/35+64 = 17 13/35 miles to go after 47 minutes

= about 17.3 miles left