Question

mammal age of hide that contains 70% of original amt of c-14

Answer 1

Run that by me again? I feel like a part of the info needed to answer the question, as well as the actual question is missing.

Answer 2

I think the question is find the age of the mammal if it's hide contains 70% of its Carbon-14, so this is a carbon-dating question, which involves, if I recall, logarithms?
Assuming the half-life of Carbon-14 is 5730 years, then the answer is as follows

Given
\[0.7=1(0.5)^{x/5730}\]
Log both sides (with the Common, base 10 log)
\[\log(0.7)=(x/5730)\log(0.5)\]
Divide both sides by log(0.5)
\[0.515=x/5730\]
Multiply both sides by 5730 to get...
\[x=2948.5\]

So your answer /should/ be 2948.5 years.
Hope this helps!