Write the reaction responsible for the solution being basic. Do not include spectator ions. With NaF being the salt that produces a basic solution in water

When NaF dissolve in water, it completely dissociates into Na⁺ and F⁻. The sodium ion that is Na⁺ do not react with water while the fluoride ion reacts with water and form hydrogen fluoride and hydroxide ion.

That can be shown in the reaction:

F⁻ + H₂O--->HF + OH⁻

Also using thumb rule it can be predicted that when salt containing anion of weak acid and cation of strong base, dissolve in water, basic solution is produced.