The following formulas and definitions are essential to address the questions.
Displacement is defined as the shortest distance between a particle's initial and final positions.
Average speed V_a = \frac{\text{ total distance }}{\text{time }}
Average velocity v_a = \frac{\text{ displacement }}{\text{time }}
Given that

Displacement = 10 km
Total distance = 23 km
Total time taken by the taxi to reach hotel, t = 28 min
a)
Average speed V_a = \frac{\text{ total distance }}{\text{time }}
V_a = \frac{23 km}{28 min}
V_a = 0.82 km/min
V_a = 0.82 * 60 = 49.29 km/h
b)
Average velocity v_a = \frac{\text{ displacement }}{\text{time }}
v_a = \frac{10}{28}
v_a = 0.357 km/min
v_a = 0.357 *60 = 21.43 Km/h
Hence, The value of the average speed is not equal to the average velocity.