Write a linear equation that describes the value y (in dollars) of the mri machine in terms of the time t (in years), 0 ≤ t ≤ 9.

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.
 
 y = a * t + b with t [0, 9]

the image of (6, 9) under a dilation is (4, 6). the scale factor is

b. 2/3

You have 2 sides that are 2 cms and you have 6 sides that are 1/2 cm and you have 4 sides that are 1 cm. the smallest sides are 1/2 the medium sized sides are 1 and the smallest are 1/2. so to find the perimeter you have to add them all up together so your answer will be 11 cm's