In a right triangle (and only there!) the length of the median of the hypotenuse is the half of the hypotenuse. Calculate the hypotenuse first using Pythagorean theorem.
I've got 10.
Therefore the length of the median is 5.
In a right triangle (and only there) the altitude h can be calculated by:
with a, b as legs and c as hypotenuse.
With your question you'll get h = 4.8