if a egyptian mummy has 61% carbon-14 how long ago was it buried?

Question

Take a 100 g initial sample. Now there are 61 g C-14.
Use ln(No/N) = kt
where No = 100
N = 61

You will need k and you may obtain that from k = 0.693/t_1/2.
Look up t_1/2 and substitute in that equation to find k, then substitute k in the first equation I listed. Post your work if you get stuck.