A) She wants to earn $2000 and work 150 hour so the rate will be the divirion so:

So she should charge customers $13.33 dollars per hour
B) now she just can work 100 hour so the new rate will be:

So now she should charge $20 dollars per hour.
C) In this case the rate will be the slope so we can write an equation like:

D) in this equation we can see that x is inverse to y so the bigger become x, y will be shorter and if x is a low number the y will increase.