There is an isosceles triangle.
The triangle is like two right triangles put together.
To find out the height of the triangle, we remove the other right triangle and we use the other triangle to find the height using the Pythagorean theorem.
Phytagoras Theorem :
b² = c² - a²
x² = 8² - (6÷2)²
x² = 64 - 3²
x² = 64 - 9
x² = 55
x = √55
So, the value of x is √55 (B)
Hope it helpful and useful :)