what is the acute angle between the hands of hour and minute at 6:25?

The minute hand has advanced 25/60 = 5/12 of a circle, or 150°

The hour hand at 6:00 is at 180°, and it has advanced 5/12 of the way to the 7, or 5/12 * 30 = 12.5°

So, the angle is 12.5+30 = 42.5°