Answer:
B
Step-by-step 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 = 3² + 7² = 9 + 49 = 58 ( take square root of both sides )
x = [tex]\sqrt{58}[/tex] → B
