Aloha :)
$$\left.\mathrm{DIN}=1+10\cdot\lg(\mathrm{ASA})\quad\right|\;-1$$$$\left.\mathrm{DIN}-1=10\cdot\lg(\mathrm{ASA})\quad\right|\;:10$$$$\left.\frac{\mathrm{DIN}-1}{10}=\lg(\mathrm{ASA})\quad\right|\;10^\cdots$$$$\left.\mathrm{ASA}=10^{\frac{DIN-1}{10}}=10^{0,1\cdot(\mathrm{DIN}-1)}\quad\right.$$