The answer is A.
A is correct because...
(7z+23)-(15z+9) There's an invisible positive 1 in front of (7z+23). Distribute.
7z+23-(15z+9) Distribute the negative sign among 15z and 9.
7z+23-15z-9 Now, combine the like terms, 7z, and -15z. 7z - 15z
-8z+23-9 Combine the like terms, 23 and -9. 23 - 9
-8z +14
