Answer:
b) Take the current height, and add up 15.
c) y = 80x + 15
where y is the height of the water in the pool, in centimeters
where x is the time since the hose is in the pool, in hours
d) 180 = 80x + 15
165 = 80x
x = 165/80 = 2.0625 hours, which is also 2 hours and 3 minutes.
