Answer:
13414 years
Step-by-step explanation:
From;
0.693/ t1/2 = 2.303/t log No/N
t1/2 = half life of C-14
t = age of the sample
No= initial amount of C-14
N = present amount of C-14
From the question, N = 0.2 No
Hence;
0.693/5700 = 2.303/t log No/0.2No
1.2 * 10^-4 = 2.303/t log 1/0.2
1.2 * 10^-4 = 1.6097/t
t = 1.6097/1.2 * 10^-4
t = 13414 years