Logarithmic Functions Practice Test

A sample decays by $A(t)=200\left(\tfrac12\right)^{t/6}$. Determine the time, in years, for $A(t)$ to reach $30$ grams using logarithms.​

A radioactive isotope has half-life $8$ days, modeled by $A(t)=A_0\left(\tfrac12\right)^{t/8}$. Determine $t$ when $A(t)=0.20A_0$ using logarithms.​