Via the half-life equation:
[tex]A_{final}=A_{initial}(\frac{1}{2})^{\frac{t}{h}}[/tex]
Where the time elapse is 11,460 year and the half-life is 5,730 years.
[tex]A_{final}=A_{initial}(\frac{1}{2})^\frac{11460}{5730} \\\\A_{final}=A_{initial}\frac{1}{4} \\\\A_{final}=\frac{1}{4}A_{initial}[/tex]
Therefore after 11,460 years the amount of carbon-14 is one fourth (1/4) of the original amount.