Well the easiest way we can do it is convert liters in to milliliters and since there are 1000 milliliters in a liter multiply 1458 by 1000 and 487 by 1000 which will get you 1458000 milliliters of capacity and the 487 liters turns into 487000 mililiters we add this to the 750 milliliters to get 487750 milliliters. Now it is all a matter of subtracting to find out how much more needs to be put in. 1458000-487750=970250 milliliters. So the amount needed to fill the hot tub is 970250 ml or if you want to convert it back to liters 970.250 l
