Verified answer

we know

[tex]if \: loga = b \: \: we \: have \: \: {10}^{b} = a [/tex]

hence

[tex]log(3x + 1) = {2}^{2} \\ \\ 3x + 1 = {10}^{ {2}^{2} } \\ \\ 3x + 1 = {10}^{4} \\ \\ 3x + 1 = 10000 \\ \\ 3x = 9999 \\ \\ x = \frac{9999}{3} \\ \\ x = 3333[/tex]