first, let me write the expression
[tex](4x^3-4+7x)-(2x^3-x-8)[/tex]
So, the "-" minus before a parenthesis change the signs of the numbers that are inside, so: (and then the parenthesis can go away)
[tex]4x^3-4+7x-2x^3+x+8[/tex]
now we can sum or subtract the numbers with the same x, so we can sum the 4x^3 with the -2x^3, the 7x with the x, and the -4 with the 8
so we have
[tex]\begin{gathered} (4-2)x^3+(7+1)x+(8-4) \\ 2x^3+8x+4 \end{gathered}[/tex]
So the answer is: Option B
