Form a right triangle, with the base being the distance between the trees, 11 meters.
The height would be the difference between the height of the two trees: 29-12 = 17 meters
Now using the Pythagorean theorem calculate the hypotenuse, which would be the distance between the tops:
X ^2 = 11^2 + 17^2
X^2 = 121+ 289
X^2 = 410
X = sqrt(410)
X = 20.24845
The distance is:
Exact answer = sqrt(410) meters
Decimal answer = 20.24845 meters (round the answer as needed)