A moving sidewalk has a velocity of 1.7 m/s north. If a man walks south on the sidewalk at a speed of 1.1 m/s, how long does it take him to travel 15 m north in relation to a stationary observer

Sorry i don’t know what to do

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.