Answer: 8 mm
Explanation:
The altitude of the triangle can also be known as the "height" from the highest point as a straight line perpendicular to the opposite side (the "bottom" which is also known as the "base" of the triangle).
This altitude makes two right triangles, so we will use the Pythagorean theorem to help us solve.
a² + b² = c²
a² + (6)² = (10)²
a² + 36 = 100
a² = 64
a = 8
The altitude of this triangle is 8 mm.