Answer:
√7 ≈ 2.646
Explanation:
The triangle apparently has two sides of length 4 and a third side of length 6. The altitude of the triangle will divide the long side in half, making that half one leg of the right triangle with hypotenuse 4.
The altitude of interest is then the length of the other leg:
√(4² -3²) = √7 ≈ 2.646