The number would be 12. If you substitute you will find that 12 is correct.
Let's use the SAS postulate! SAS means Side, Angle, Side. I would sometimes write this the other way and get in trouble, haha.
It technically means if a triangle that has a congruent angle between two congruent sides, it means it is congruent. Here is a picture.
Angles 1 and 3 are vertical lines and because they are vertical, both angles equal each other.
Answer:
x=-2
Step-by-step explanation:
branliest pls