Given,
The boat covers 14 km upstream and 20km downstream . at time 7 hours
also cover 22km ups. and 34km dwn in10 hours
total speed = total distance/total time
:.total distance = 14+20+22+34=90km
and total time=7+10=17 hours
by formula
speed=90/17
=> 5.294km/h
=> 5.294km/h the speed of boat in still water is 5.29 km/h