Which expression is a perfect cube? a. x^8 b. y^24 c. m^28 d. s^64

B is your answer because when you take 24/3=8 but when you take 8/3 or 28/3 or 64/3 you will get a decimal. 

The answer is A

Try breaking down each solution into cubic form.

A) a^8 = ((a^2)^3) (perfect cube because 2 is a prime number)

B) a^24 = (((a^2)^3)^2) (not a cube because of the 2)

C) a^28 = ((a^2)^2)^7 (not a cube because of 7)

B) a^64 = (((a^2)^32) (not a cube since 32 is not a factor of 3)

Hope I helped :)