Answer:
B,C,D
Explanation:
B.
(15/3)^x can be simplified to 5^x because 15/3 = 5 and the power remains same after we simplify
C.

after rewriting the expression we can simplify 3^x from bottom and top so only 5^x remains.
D.
to multiply an exponential number you can add up their powers if their bases are same.