Respuesta :

sqdancefan

Answer:

12x -6

Step-by-step explanation:

Assuming these are segments on the same line with B between A and C, the segment addition postulate says ...

... AC = AB + BC

... AC = (5x +3) + (7x -9)

... AC = x(5+7) +(3-9)

... AC = 12x -6