1 liter is equal to 1000 milliliters. So, 1.75 liters is equal to 1750 milliliters. To subtract 750 milliliters from 1750 milliliters, we can simply subtract the two numbers:

1750 milliliters - 750 milliliters = 1000 milliliters

Therefore, 1.75 liters minus 750 milliliters is equal to 1000 milliliters, which is also equal to 1 liter.