Question 1092089
Let s be the speed of Jane's boat in still water. Then:
.25(s-4)=.2(s+4)  (.25=1/4 hour=15 min; .2=1/5 hr=10 min)
.25s-1=.2s+.8
.05s=1.8
s=36
Jane's boat goes 36 kmh in still water 
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