The correct answer is 9.
Because they share a common angle at the top, we know that we can create a proportion using similar sides.


Now we can cross multiply to solve.
12*6 = 8*x
72 = 8x
9 = x
Your answers are -10 and 4
-10+4=-6
The equation would equal Axf+f
Answer:
you want to isolate x so just add 16 to the right side (-4)
so -16 + x = -4
+16 +16
x=12
hope this helps :)