Given:
Alvin paddled for 2 hours with a 5-km/h current to reach a campsite.
Let n be the speed of boat.
Distance is calculated as,
[tex]\begin{gathered} d=rt \\ d=2\mleft(n+5\mright) \end{gathered}[/tex]The return trip against the same current took 7 hours.
[tex]\begin{gathered} d=rt \\ d=7(n-5) \end{gathered}[/tex]Equate both the equations,
[tex]\begin{gathered} 2(n+5)=7(n-5) \\ 2n+10=7n-35 \\ 7n-2n=10+35 \\ 5n=45 \\ n=\frac{45}{5} \\ n=9 \end{gathered}[/tex]Answer: the speed of the boat is 9 mph.
