For this case you could write a generic linear equation that determines the value in dollars after a number of years corresponding to the interval [0, 9]. Writing the equation we have
y = a * t + b with t [0, 9]
where,
a and b with constants that belong to the real numbers
t: it's time in years
y: the value in dollars of the mri machine.
answer:
y = a * t + b with t [0, 9]
