Question 173294
Let {{{z=sqrt(2)}}}



So the expression {{{2*sqrt(2) + 8*sqrt(2)- sqrt(2)}}} becomes {{{2z + 8z- z}}} 



Now combine like terms to get {{{9z}}}. 



Now replace "z" with {{{sqrt(2)}}} to get {{{9*sqrt(2)}}}



So {{{2*sqrt(2) + 8*sqrt(2)- sqrt(2)=9*sqrt(2)}}}