A29 gram sample of a substance that's used to preserve fruits and vegetables has a k-value of 0.1359. find the substance's half life in days. round to nearest tenth

Okay well
a(t)= amount of substance remaining after t days
assuming exponential decay, a(t)=29e^-0.1359t

now, find the half, set a(t)= half the original and solve for t

14.5=29e^-0.1359t
0.5=e^-0.1359t
In(0.5)=In(e^-0.1359t)
In(0.5)=-o.1359t

t=in(0.5)/(-0.1359)= (aprox) 5.1 days