How do you change 2.11 into a mixed number in simplest form

What is the missing constant term in the perfect square that starts with x^2 -20x

Water flows at a steady rate from a tap. its takes 40 seconds to fill a 4 litre watering can from the tap. the rate at which water flows from the tap is halved. complete: 4 litres into cm3

What’s -11-33k and factor each expression completely