Chapter 12 - Section 12.8 - Exponential and Logarithmic Equations and Problem Solving - Exercise Set - Page 896: 15

{$11$}

$\log_{2} (x+5)=4$ $x+5=2^{4}$ $x+5=16$ $x=16-5=11$ Checking the answer by inserting it in the original equation: $\log_{2} (11+5)=4$ $\log_{2} (16)=4$ $\log_{2} 2^{4}=4$ $\log_{2} 2^{4}=4$ $4\log_{2} 2=4$ $4=4$ Therefore, the solution set is {$11$}.