Clock Angle at 3:15

The minute hand points at $3$, i.e. $90°$.

The hour hand moves $0.5°$ per minute.

1. 1. Positions

   Minute hand: $90°$. Hour hand: $90°+15(0.5°)=97.5°$.

2. 2. Angle

   $$97.5^{\circ }-90^{\circ }=7.5^{\circ }$$

3. 3. Key idea

   Remember the hour hand keeps moving between hour marks.

Answer: 7.5