Question

A man who can row in still water at 3 mph heads directly across a river flowing at 7 mph.

Answer 1

He drifts downstream at the river's speed, 7 mph. He has a 3 mph component across the river.

His direction with respect to the heading angle (straight across) is

tan^-1 7/3 = 66.8 degrees (towards downstream)

hope this helps :)