3& 4, and tell explanation
(p. s: sorry for my sloppy handwriting)

3) Altitude / Time = y2 - y1 / x2 - x1 = 30 - 60 / 6 - 3
 m = -30 / 3
 m = -10

In short, constant rate of change is y = -10x

b) Constant proportionality exists between two quantities, as the amount of changing in Altitude over fixed period of time is same (constant) for every instance. 

4) Sales / Day = y2-y1 / x2-x1 = 2,000 - 1,000 / 6 - 3
m = 1000 / 3
m = 333.3

a) In short, Constant relationship is y = 333.3x

b) Constant proportionality exists between two quantities, as the amount of changing in Sales over fixed days is same (constant) for every instance. 

Hope this helps!