I need some help, i do not know if I am doing this right - Please help. Class is CRIJ 4377 Elementary Statistics in Criminal Justice Research.

The rate of change = (100)(time 2f - time 1f / time 1f)

Question: The 2018 cohort of juveniles in a new diversion program consisted of 400 participants. Of this cohort, 240 graduated early. If the number of early release from the 2017 cohort of the same size was 200, what is the early-release rate of change between 2018 and 2017?

Here is how I solved it, please tell me if I am right or wrong and if I am wrong, please help me to find the correct way to solve this problem.

(400) (200-240/240) or is it (100)(240-200/200)

= (400)(-40/240) = (100)(0.20)

= - 66.7 = 20

Im just confused.