Answer
$-x^{2}+8x-1$
Work Step by Step
Subtract the polynomials inside the brackets
$ \begin{array}{rrrrrr}
& 10x^{3} & -5x^{2} & +4x & +3 & \\
-( & -3x^{3} & -4x^{2} & +x & & )\\
\hline & & & & & \\
= & (10+3)x^{3} & +(-5+4)x^{2} & +(4-1)x & +3 & \\
& & & & & \\
= & 7x^{3} & -x^{2} & +3x & +3 & \\
& & & & & \\
& & & & &
\end{array}$
From this difference, subtract the third polynomial.
$ \begin{array}{rrrrrr}
& 7x^{3} & -x^{2} & +3x & +3 & \\
-( & 7x^{3} & & -5x & +4 & )\\
\hline & & & & & \\
= & (7-7)x^{3} & +(-1-0)x^{2} & +(3+5)x & +3-4 & \\
& & & & & \\
= & & -x^{2} & +8x & -1 & \\
& & & & & \\
& & & & &
\end{array}$
$=-x^{2}+8x-1$
