Chapter 4 - Exponential and Logarithmic Functions - Section 4.4 Logarithmic Functions - 4.4 Assess Your Understanding - Page 322: 89

$\dfrac{7}{2}$

$\because y=\log_a x \text{ is equivalent to } x= a^y$ $\therefore 3 = \log_2{(2x+1)} \text{ is equivalent to } 2x+1=2^3$ Solving for $x$ gives \begin{align*} 2x+1&=2^3\\ 2x+1&=8\\ 2x&=7\\ x&=\dfrac{7}{2}\end{align*}