What is the molality of a solution prepared by adding 1.0 mol of sodium chloride to 2.0 kg of water?

You need to know the molar mass of NaCl: 58,44 g.
If 3 kg of water contain 200 g NaCl, 1 kg contain 66,66 g.
58,44 g--------------------------1 mol
66,66 g--------------------------x
x = 66,66/58,49 = 1,14 mol