Chapter 4 - Exponential Functions - 4.2 Comparing Exponential and Linear Functions - Exercises and Problems for Section 4.2 - Exercises and Problems - Page 156: 34

$x\in(-0.587,4.911)$

The best approach is to make a plot of both $f(x) = 12+20x$ and $g(x) = 0.5(3)^x$. The graph shows that the two functions intercept twice: at $x\approx -0.587$ and $x\approx 4.911$. We see that the graph of $g(x)$ lies below the graph of $f(x)$ for $x\in(-0.587,4.911)$.