Question

The speed of the current is 7 mph. The boat travels three times slower against the current than with the current. What is the speed of the boat in still water?

Answer 1

let
x--------> the speed of the boat in mph

we know that
going upstream the speed is x-7
going downstream the speed is x+7

let the distance be d
time to go upstream = d/(x-7)
time to go downstream = d/(x+7)

time going upstream is 3 times going downstream
so
3d/(x+7) = d/(x-7)
divide by d
3/(x+7) = 1/(x-7)
3x-21 = x+7
2x = 28
x = 14

the answer is
the speed of the boat in still water is 14 mph