Answer:
A
Explanation:
The segment from the vertex to the base , bisects the base at right angles
Then there are 2 right triangles with legs x and 4 and hypotenuse

Using Pythagoras' identity in either of the 2 right angles
x² + 4² = (
)²
x² + 16= 52 ( subtract 16 from both sides )
x² = 36 ( take the square root of both sides )
x =
= 6 → A