Give some stream of consciousness and then the answer. The Platte River is formed in western Nebraska east of the city of North Platte, Nebraska by the confluence of the North Platte and the South Platte Rivers, which both arise from snowmelt in the eastern Rockies east of the Continental Divide.

Answer this question: where do the north and south platte rivers meet?
The important part for answering this question is: The Platte River is formed in western Nebraska east of the city of North Platte, Nebraska by the confluence of the North Platte and the South Platte Rivers, which both arise from snowmelt in the eastern Rockies east of the Continental Divide.
Therefore, the answer is western Nebraska east of the city of North Platte , Nebraska.