Question 761976
the speed the crew can row in still water=x yards per minute say
the speed of the current is 80 yards per minute
the speed in down stream= x+80 & the distance traveled is 8000 yards
so time taken=8000/(x+80)
& in up stream=x-80 & the distance traveled is 6000 yards
so time taken=6000/(x-80)
the crew can row 6000 yards up stream in the same time it takes them to cover 8000 yards downstream. 
so 8000/(x+80)=6000/(x-80)
or 4(x-80)=3(x+80)
or 4x-320=3x+240
or x=320+240=560 
so the speed the crew can row in still water=560 yards per minute say