Answer;
10
Explanation:
from the question we observed that the shape is a right angled triangle.
and according to Pythagoras theorem, In a right angled triangle the square of the hypothenus is equal to the square of the sum of the other two side
hypothenus = 10
10^2= 8^ + X^2
100= 64 +X^2
X^2 = 100-64
X^2 = 36
X = √36
X= 6