Let the speed of the boat be x so going against the current the speed is x-7
going with the current the speed is x+7
let the distance be d
time = distance / speed time to go against the current = d/(x-7)
time to go with the current = d/(x+7)
time going against the current is 3 times going <span>with the current </span> d/(x-7) = 3d/(x+7)
⇒⇒⇒ divide by d 1/(x-7)
= 3/(x+7) x+7
= 3(x-7) x+7 = 3x - 21 2x = 28
x = 14
So, the speed of the boat in still water is = 14 mph
