y = 2.5x + 50.....with y being the total liters in the tank and x being the number of seconds
when total liters is 765....so sub in 765 for y and solve for x
765 = 2.5x + 50
765 - 50 = 2.5x
715 = 2.5x
715 / 2.5 = x
286 = x <==== so it would take 286 secondsĀ