arithmetic - a boat covers a certain distance downstream in i hour while it comes back in 1 hours if the speed of the stream be 3 kmph what is the speed of the boat in still water - skillgun

Let the speed of the boat in still water be x kmph. Then,
Speed downstream = (x + 3) kmph.
Speed upstream = (x - 3) kmph.
= (x+3)x1
= (x - 3)x3/2 kmph.
= 2x+6
= 3x-9
=> x = 15 kmph