Answer:
3
Explanation:
A simple way to solve this is by substituting, we start with trying 1 for x, 2+6=8, and 1+9=10. Because the two values are different, that means 1 is the incorrect value. We can try 2, 4+6=10, and 2+9=11, once again inequivalent. We finally try 3, and 6+6=12 and 3+9=12 meaning x must be 3