From the half-life for 14C decay, 5715 years, calculate the age of the shroud?

Question

The cloth shroud from around a mummy is found to have a 14C activity of 9.5 disintegrations per minute per gram of carbon as compared with living organisms that undergo 15.2 disintegrations per minute per gram of carbon.

Question: From the half-life for 14C decay, which is 5715 years, calculate the age of the shroud.

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Please help with this problem. I have no idea where to begin.

Answer 1

 how does it equal 3880?

if you divide

-(0.47)/-(1.21 x 10^-4) = 3884.3 is what i got?