Question

$3 \sqrt{3x+1}= \sqrt{18}$

Answer 1

$3 \sqrt{3x+1} = \sqrt{18} \\\\\\ (3 \sqrt{3x+1})^2 = (\sqrt{18} )^2\to\\\\ 9(3x+1)=18\to \\\\ 27x+9=18\to \\\\27x=18-9\to\\\\ 27x=9\to\\\\ x= \frac{9}{27} \to\\\\ x= \frac{1}{3}$