Answer:
B
Explanation:
Using Pythagoras' identity in the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
x² + 30² = 50²
x² + 900 = 2500 ( subtract 900 from both sides )
x² = 1600 ( take the square root of both sides )
x =
= 40 → B