To solve/simplify this all you have to do is group like terms (the x^2's with each other, the x's with each other, and the normal numbers, -8)
14x^2-8+5x-6x^2+2x
group the x^2 (add 14x^2 to -6x^2)
8x^2-8+5x+2x
group the x's together (add 5x and 2x together)
8x^2+7x-8
Your answer will be d) 8x^2+7x-8