Clock

Let 12 o'clock represent  0°....let the hands advance in a  positive angular  direction

At  3 o'clock   the hour  hand is  at 90°   and the  minute  hand is  at 0°

The hour hand  moves   15°   more   in  30 minutes.....so it is at 105°   at 3;30

And the minute hand is  at180°    at 3:30

So....the acute angle is   180 - 105  =   75°