Does salt water freeze faster or water?

'Faster' is not the correct Word.

Salt Water freezes at a lower temperature than pure water. (aqua puris).

Salt water also boils at a higher temperature than pure water.

There is a whole lot of chemistry dealing with the depression of freezing point, when a pure solvent is made into a solution with the dissolution of a solute.

Pure water has nothing dissolved in it.

Salt water is pure water (Solvent), with a quantity of salt (solute) dissolved in it. to form a solution.

Freezing point of pure water is 0 oC

Freezing point of saline water is ' -6 oC'.

There is a whole lot of chemistry dealing with Cryoscopic Constants.