Question 107291
First let's do some substitution
{{{2*sqrt(27)=2sqrt(9*3)=6*sqrt(3)}}}
{{{sqrt(12)=sqrt(4*3)=2*sqrt(3)}}}
Now let's get to the equation,

{{{3*sqrt(3)+2*sqrt(27)-sqrt(12)=3*sqrt(3)+6*sqrt(3)-2*sqrt(3)}}}
{{{3*sqrt(3)+2*sqrt(27)-sqrt(12)=(3+6-2)*3sqrt(3)}}}
{{{3*sqrt(3)+2*sqrt(27)-sqrt(12)=7*sqrt(3)}}}