Answer
$14x^{3}-4.7x^{2}+5.3$
Work Step by Step
$ \begin{array}{llll}
& 7.9x^{3} & -6.8x^{2} & +3.3\\
+ & 6.1x^{3} & -2.2x^{2} & +7\\
+ & & 4.3x^{2} & -5\\
\hline & & & \\
= & 14.0x^{3} & +(-9.0+4.3)x^{2} & +10.3-5\\
& & & \\
= & 14x^{3} & -4.7x^{2} & +5.3\\
& & & \\
& & &
\end{array}$