rate of change is the slope
slope = (y2-y1)/(x2-x1)
m= (180-120)/(3-2)
m = 60/1
m = 60
b. point slope form
y-y1 = m(x-x1)
y-120 = 60 (x-2)
c see attached graph. x>=0 since it is hours
d the y intercept is
y -120 = 60x-120
add 120 to each side
y = 60x
