SOLUTION: Jim is taking a canoe in the Grand River. The speed of the current is 3 miles per hour. Jim can canoe 4 miles upstream in the same time that it would take him to canoe 10 miles d

                SPEED   TIME       DISTANCE
UPSTREAM        r-3     4/(r-3)       4
DOWNSTR         r+3     10/(r+3)     10

Correct answer: 

Ignore all other RIDICULOUS and NONSENSICAL answers! 

Let "u" be the unknown the speed of Jim’s canoe in still water.

Then the speed canoeing downstream is (u+3) miles per hour (the speed relative to the bank of the river), 
while the speed canoeing upstream is (u-3) miles per hour.

The time Jim spends canoeing 4 miles   upstream is 4/(u-3) hours.
The time Jim spends canoeing 10 miles downstream is 10/(u+3) hours.

According to the condition, these amounts of time are the same.
It gives you an equation

 = .

To solve it, multiply both sides by (u-3)*(u+3). You will get

4*(u+3) = 10*(u-3),

4u + 12 = 10u - 30,

12 + 30 = 10u - 4u,

6u = 42  --->  u =  = 7.


Answer.  The speed Jim canoes in still water is 7 miles per hour.