Question 1075479
The half-life of a specimen is defined as the length of time it takes to lose half of its original mass. In this case, there is only 15% of the normal carbon-14 left. So:
.15=(.5)^t/5600 where t is age of the fossil, in years.

First, calculate for the single value:
.15=.5^t
log 0.15=log 0.5^t
log 0.15=t log 0.5
t=log 0.15/log 0.5=2.7369655941662061664165804855416
Then multiply by 5600:
5600 x 2.7369655941662061664165804855416=15,327 years as the approximate age of the fossil. ☺☺☺☺