Answer: 6√6
Step-by-step explanation: When an angle is 45 degrees in a triangle it is actually half a square (I know right!!!), so, therefore, the other side length will also be 6, and then using the Pythagorean theorem we get the hypotenuse to be 6√2. Now, when an angle is 60 degrees in a triangle it is actually half an equilateral triangle (I know right!!!), so, therefore, the other side length will be double the length, 12√2, and using the Pythagorean theorem we get the side length x to be 6√6! Hope this helps!