Because the rope wraps around the tree 4 times, leaving 5 meters; It's more than 3 meters around 6 times.

5-3=2 meters

2÷2= 1

The difference between the front and back is 2 laps, and the length difference is 2 meters. It means that the rope goes around the tree 1 meter.

Rope length: 4× 1+5 = 9m.