So you want to be able to see the increase and the amount of time that the increase happened in so you subtract 40,000 from 64,000 and 1990 from 1998
64,000-40,000= 24,000
1998-1990=8
Now you have the profit increase and the number of years. Time is always your y value, and to find the rate of change you put your x over your y.
24,000/8
Now you have your rate of change as a fraction but that fraction can be simplified. To do this you divide x by y
24,000/8= 3,000
Your rate of change is $3,000 per year.
