First, divide through by 180.
[tex]\frac{y}{180}\text{ = }\frac{180(1.305)^x}{180}[/tex][tex]\begin{gathered} 1.305^{x\text{ }}\text{ = }\frac{y}{180} \\ \text{Next, take the logarithm of both sides} \\ Log^{1.305^x}=Log^{\frac{y}{180}}\text{ } \\ \text{xLog}^{1.305}=Log^{\frac{y}{180}} \\ r\text{ = }\frac{Log^{\frac{y}{180}}}{Log^{1.305}^{}} \\ r\text{ = }\frac{Log^{\frac{y}{180}}}{0.11} \\ r=8.65Log^{\frac{y}{180}} \end{gathered}[/tex]