The number of asthma sufferers in the world was about 84 million in 1990 and 130 million in 2001. Let N represent the number of asthma sufferers (in millions) worldwite t years after 1990.
Since "t = 0" means "in 1990", then the two points they've given you are (t, N) = (0, 84) and (t, N) = (11, 130). So your slope
value is fine, but should probably be left as an improper fraction: m = 46/11.
To find the line equation
, try plugging the y-intercept, (t, N) = (0, 84), into the slope-intercept form, y = mx + b. (By changing the meaning of "t", you created a relationship which didn't "look right" in the context of the exercise.)
b. Write N as an exponential function of t. What is the growth factor? What does it tell you about asthma sufferes?
Try using the given definition of "t", as illustrated above, to get the required equation.