The hour-hand moves 360° in 12 hours = 0.5° per minute. Time elapsed = 35 minutes. Angle swept = 35 × 0.5° = 17.5° = 35/2°.
(b) $\dfrac{35}{2}°$
The hour-hand completes 360° in 12 hours (720 minutes), so it moves 360/720 = 0.5° per minute. From 7:20 to 7:55 is 35 minutes, giving 35 × 0.5° = 35/2°. The length of the hand (6 cm) is a distractor — it is irrelevant when only the angle is asked.