The correct option is D 3
Let the number be x and another number be y then according to question,
x3=8×y3⋯(i)
and the sum of their cubes is 243,
⇒x3+y3=243⋯(ii)
Now, from equation (i) and equation (ii) we get,
8y3+y3=243⇒9y3=243⇒y3=2439=27⇒y=3
Now, for x let's put the values of y in equation (i).
x3=8×33⇒x3=2×2×2×3×3×3⇒x=2×3=6
Now, as required in the question, let's take the difference of the two numbers.
⇒ x−y=6−3=3
Hence, option 'a' is correct.