It's 6. The Pythagorean Theorem details how to find the length of a right triangle's hypotenuse.
The equation is a² + b² = c²
C is the length of the hypotenuse. The side lengths you have are a leg as 8 and hypotenuse as 10. By substituting these values into the equation, we get 8² + b² = 10²
Therefore, 64 + b² =100
So b² = 36
By square rooting both sides we finally reach the answer b=6.
