Chapter 5 - Exponential and Logarithmic Functions - 5.3 One-to-One Functions; Inverse Functions - 5.3 Assess Your Understanding - Page 282: 80

$x=0.5$

The base is same on the 2 sides on the equation (and it is not 1), hence they will be equal if the exponents are equal. Hence \begin{align*}3x=2-x\end{align*}Add $x$ to both sides:\begin{align*}4x=2\end{align*}Divide both sides by 4: \begin{align*}x=0.5.\end{align*}