Question 599500
You are doing it right but made a mistake in understanding the question

actually sqrt(3) is multiplied with sqrt(6) only and not with sqrt(8)

sqrt(3)*(sqrt(6)-sqrt(8)

=
{{{sqrt(18)-sqrt(8)}}}

which simplifies to
{{{sqrt(9)*sqrt(2)-sqrt(4)*sqrt(2)}}}

which is equal to

{{{3*sqrt(2)-2*sqrt(2)}}}

i.e. sqrt(2)