The given expression \(\frac{z}{12}\) -9 can be an integer only if \(\frac{z}{12}\) is an integer. \(\frac{z}{12}\) is an integer only when z is divisible by 12.
From statement I alone, we have \(\frac{(z+24)}{12}\) = integer. This can be written as z+24 = 12*integer.
The number on the RHS is a multiple of 12 and so is 24. Therefore,
z = 12*integer – 24 which means that
z is essentially a multiple of 12.
Since z is a multiple of 12, \(\frac{z}{12}\) will be an integer. Therefore, \(\frac{z}{12}\) – 9 will also be an integer. Statement I alone is sufficient to answer the question with a unique YES. Answer options B, C and E can be eliminated. The possible answer options are A or D.
From statement II alone,
z is a multiple of 6. But, this
does not mean that
z is necessarily a multiple of 12. Therefore, \(\frac{z}{12}\) -9 is not necessarily an integer always and so we will get a YES AND a NO. Statement II alone is insufficient. Answer option D can be eliminated.
The correct answer option is A.
Hope that helps!