The answer provided by Arturo is certainly the conventional way to solve this problem, and is absolutely correct. But for those of us who are somewhat "mathematically challenged", I find it easier to do it as follows:
fraction remaining = 0.5^n where n = the number of half lives that have elapsed.
Here the fraction remaining = 0.5429 and we can solve for n
0.5420 = 0.5^n
log 0.5420 = n log 0.5
-0.26529 = -0.301n
n = 0.8814 which is the number of half lives that have elapsed since burial
Since 1 half life = 5730 years...
5730 yrs x 0.8814 = 5,050 years
Just another way to do these kinds of problems. I can never remember the equation A(t) = A0e-kt, so I use this.