Question 982494
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Distance between two places stays the same:
D=distance 
Rate downstream is rowing+current=y+x
Rate upstream is rowing-current=y-x
Distance=rate x time
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Upstream:
D=(y-x)(4hrs)
Downstream:
D=(y+x)(3hrs)
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Since D=D:
(y-x)(4hrs)=(y+x)(3hrs)
(4y)hrs-(4x)hrs=(3y)hrs+(3x)hrs
(y)hrs=(7x)hrs Divide each side by 1 hour.
y=7x