The first step to finding the equation of a line when 2 points are known.... the first step would be to use the slope formula to find the slope of the line
You are told that sprinklers run for the same amount of time. lets refer to this time as T. you are told that 4 sprinkles run one at a time for 50 minutes total. that means that T should be 50/4 = 12.5 minutes = 12 minutes and 30 seconds