Answer:
x = 8
Explanation:
The given is a right triangle and in right triangles the square length of the hypotenuse is equal to sum of square length of the legs:
10^2 = x^2 + 6^2 calculate the powers
100 = x^2 + 36 subtract 36 from both sides
64 = x^2 find the root for both sides
8 = x