To find the zeros of a polynomial, you make every factored parentheses equal to zero. You basically make the other side equal to zero and solve for x.
So,
[tex]f(x)=(x-9)(x+12)(x-24)\\0=(x-9)(x+12)(x-24)\\x-9=0\\x=9\\x+12=0\\x=-12\\x-24=0\\x=24[/tex]
Your zeros are x = 9, -12, 24
So your answer is 3) 9, -12, 24