this question has been posted several times... a little research could be a good idea....

so, 450y=n^3, therefore 450 and Y must have triplets....
breakdown 450= 2*5*5*3*3.... which is equal to 2*5^2*3^2

for n^3, 450 must be multiplied by an integer that has 2, 5 and 3 to make all numbers squared to the third... threfore y must be 2^2*5*3....

hence the only integer in the options give is Y/2^2*5*3 (which would be equal to 1)....

So basically you're looking for the answer that completes the cube. Got it. Awesome, thanks so much.

Will do a search next time.