A person walks from one end to the other of a 100-meter long moving walkway at a constant rate in 50 seconds, assisted by the walkway. When this person reaches the end, they reverse direction and continue walking with the same speed, but this time it takes 150 seconds because the person is traveling against the direction of the moving walkway. If the walkway were to stop moving, how many seconds would it take this person to walk from one end of the walkway to the other?  Answers
A) 63 B) 66 C) 69 D) 72 E) 75

Rationale: let v be the speed of the person and let x be the speed of the walkway . 50 ( v + x ) = 100 then 150 ( v + x ) = 300 150 ( v - x ) = 100 when we add the two equations : 300 v = 400 v = 4 / 3 time = 100 / ( 4 / 3 ) = 75 seconds the answer is e .
Answer: E