Question 11655
First, think of the expression (2x^2+8x-7) as a number, a single number. Let's call it c. The first expression is (3x-5) which can be written (a+b).
What you have is (a+b)c. This, of course, is ac + bc. 
Now put back what a, b, and c stand for.
You should get {{{3x(2x^2+8x-7) - 5(2x^2+8x-7)}}}
Can you do these two multiplications?
{{{3x(2x^2+8x-7)=6x^3+24x^2-21x}}}
{{{5(2x^2+8x-7)=10x^2+40x-35}}}
The whole thing looks like {{{(6x^3+24x^2-21x)-(10x^2+40x-35)}}}
Which is {{{6x^3+24x^2-21x-10x^2-40x+35=6x^3+14x^2-61x+35}}}