What is the slope of the line which passes through the points (3,-8 and (-1,0)?

What is the value of x? enter your answer in the box. photo attached.

An architect is designing a water fountain for a park she uses the given function to model the water jet flowing from the fountain nozzles where h(x) gives the height of the water jugs in feet x feet from the starting point h(x)=-1/20x+x+15

What could explain what happened when the time was equal to 120 minutes