Explanation:
V(m,b)= V(m,e) - V(b,e)
2.3m/s (west) = V(m,e) - 15m/s (east)
to solve this change the direction of slower speed. so it will become negative value
-2.3m/s ( east) = V (m,e) - 15m/s (east)
V(m,e) = 15m/s (east) - 2.3m/s (east)
V(m,e) = 12.7 m/s (east)
velocity of the man in frame of reference of stationary observer is 12.7 m/s
it's slightly less than the velocity of bus so stationary observer see the man move slower than the one inside the bus
ps:- V(m,b) - velocity of man relative to bus
V(b,e) - velocity of bus relative to earth
V(m,e) - velocity of man relative to earth