Pre calc question I am struggling with

Question

The​ half-life of​ carbon-14 is 5600 years. If a piece of charcoal made from the wood of a tree shows only 67​% of the​ carbon-14 expected in living​ matter, when did the tree​ die?

Answer 1

so half-life of Carbon can be written under the following formula:

C(t)=(1/2)^t/5600

Now based on the question 67% or .67 of the original Carbon is left, so we need to plug this number into C(t) and then solve for t:

.67=(1/2)^t/5600, (ln both sides) ln.67=ln(1/2)^t/5600, ln.67=(t/5600)ln.5, (multiply by 5600 and divide by ln.5)

t=5600ln.67/ln.5=3235.5 years ago