Question 31355
{{{ (5x^2-3x+2)+(-3x^2-5x-8)-(x^2+3x-10) }}}
First thing is to distribute the understood +1 and -1 that sit in front of the parentesis. 
When doing this with +1, you can just drop the parenthesis.
But with the -1 it changes the signs of everything within the parenthesis.
It will look like this:
{{{ 5x^2-3x+2-3x^2-5x-8-1x^2-3x+10 }}}
Combine like terms,  Start with the x^2
{{{ x^2-3x+2-5x-8-3x+10 }}}
next the x quantities
{{{ x^2-11x+2-8+10 }}}
and finally the constants
{{{ x^2-11x+4 }}} DONE!