What amount of ice must be added to 540.0 g of water at 25.0 °C to cool the water to 0.0 °C and have no ice

Answer 1

melting ice at zero is
mass ice*heat fusion = ?
Cooling 540 g water from 25 to zero is
mass H2O * specific heat ice x (Tfinal-Tinitial). Put those together to obtain
(mass ice*heat fusion) + (mass H2O x specific heat water x (Tfinal-Tinitial) = 0
Solve for mass ice.