moles = grams/molar mass.
m = moles/kg solvent.
delta T = Kf*m
Calculate delta T.
The freezing point of the solvent, normally, is 0o C.
The freezing poing depression constant for the solvent, H2O, is 1.86 o/m. You may have rewritten the problem, but, as stated, it does not ask for the freezing point of the solution. The first three steps, however, will calculate that. The other two numbers, the normal freezing point and the freezing point depression constant can be looked up in tables.