Question 152751
{{{sqrt(27)=sqrt(3*9)=sqrt(3*3^2)=3sqrt(3)}}}

{{{sqrt(12)=sqrt(3*4)=sqrt(3*2^2)=2sqrt(3)}}}
So
{{{3sqrt(3)+2sqrt(27)-sqrt(12)=3sqrt(3)+2*3sqrt(3)-2sqrt(3)=(3+2*3-2)*sqrt(3)=7sqrt(3)}}}