Answer:
the square root of 55, or 7.42
Explanation:
Use the Pythagorean Theorem, or a²+b²=c², where a and b are the sides or "legs" of the triangle and c is the hypotenuse.
a is 3, b is x, and c is 9
If you plug that into the equation, you get 3²+x²=8²
We can make this 9+x=64 by squaring the 3 and 8.
Then we can subtract 9 from each side to get x=55.
Finally, take the square root of 55 to get √55 or 7.42.
I hope this helped!