Question 331795
distance = rate*time or speed *time

downstream the speed is Boat + current speed :  B+C
upstream the speed is Boat -current speed:  B-C
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22miles = (B+C)*t=Bt+Ct
16miles = (B-C)*t=Bt-Ct
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since C (current speed)=4
22miles =(B+4)*t=B*t+4t
16 miles =(B-4)*t=B*t-4*t
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add these two equations
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38 = 2Bt
solve for t: t=38/(2B)=19/B
subsitute t into one of the orginal equations
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22 = B(19/B) + 4(19B)
22=19+76/B

can you handled it from here, by solving for B (the boat speed in still water)?