Answer: It's 8 :)
Step-by-step explanation: Do the Pythagorean Theorem. a^2 + b^2 = c^2. In every case, c is the hypotenuse, so you do 10^2 = 6^2 + x^2. Then, it becomes 100 = 36 + x^2, then subtract 36 and you get 64. Then, you square root both sides to get 8. Have a great day!