Question 109962
Multiply the first terms in each set of parenthesis  6x and x.

You will get {{{6x^2}}}

Next. multiply the outer terms in the set of parenthesis.  6x and -8.
You will get  {{{-48x}}}

Next, multiply the inner terms in the sets of parenthesis.  -9 and x
You will get {{{-9x}}}

Next, multiply the last terms in the sets of parenthesis.  -9 and -8.
You will get {{{72}}}

Now put it all together
{{{6x^2-48x-9x+72}}}

Now combine like terms to simplify into a trinomial
{{{6x^2-57x+72}}}

I do this on paper and draw lines connecting each of the sets in order of F O I L so that I dont ever miss a step.