Let Ve = speed of escalator
Let Vm = speed of the man (Vm=0 because he is stationary)
Let Vw = speed of woman
According to the stationary observer,
Because the man stands still on the escalator, his speed is Ve = 0.2 m/s.
The speed of the woman is Ve + Vw = 0.5 m/s
Therefore
0.2 + Vw = 0.5
Vw = 0.3 m/
Answer:
The woman is walking at 0.3 m/s.