Answer:
x = 4
Step-by-step explanation:
Since the triangle is 45-90-45, x = 4.
4 is the answer
By Pythagorean theorem
hypotenuse^2=base^2+altitude^2
(4sqrt2)^2=(4)^2+x^2
32=16+x^2
32-16=x^2
16=x^2
taking square root on both sides
x=4
