Question 735078
Use the rule

{{{loga+logb=log(ab)}}}

{{{log4+log(x-1)=log(4(x-1))}}}

so {{{log(3x)=log(4(x-1))}}}

{{{3x=4(x-1)}}}
{{{3x=4x-4}}}
{{{-x=-4}}}
{{{x=4}}}