Observation: A white precipitate will form immediately upon mixing the solutions together.
Explanation: Potassium bromide (KBr) and silver nitrate (AgNO$_3$) react in an aqueous solution to form a precipitate of silver bromide (AgBr). This reaction is represented by the following equation:
KBr(aq) + AgNO$_3$(aq) -→ AgBr(s) + KNO$_3$(aq)
The silver bromide precipitate is white and will settle to the bottom of the container.