Explanation:
b = the speed of the boat in still water.
S = the speed of the stream
Relative to the bank, the speed upstream is B-S.
The speed downstream is B+S.
Use the equation for distance.
Rate * Time = Distance
Upstream
(B-S)6 = 258
(B+S)6 = 330
Simplify first:
B-S = 43
B+S = 55
Solve by elimination. Add the two equations.
2B = 98
B = 49 mi/hr
Substitute this into either equation and solve for S.
B+S = 55
49+S = 55
S = 6 mi/hr