Answer
$-\displaystyle \frac{5}{12}x^{9}+\frac{7}{15}x^{5}-1.7$
Work Step by Step
$ \begin{array}{lllll}
& \frac{1}{3}x^{9} & -\frac{1}{5}x^{5} & -2.7 & \\
+( & -\frac{3}{4}x^{9} & +\frac{2}{3}x^{5} & +1 & )\\
\hline & & & & \\
= & (\frac{1}{3}-\frac{3}{4})x^{9} & +(-\frac{1}{5}+\frac{2}{3})x^{5} & +(-2.7+1) & \\
& & & & \\
= & \frac{4-9}{12}x^{9} & +\frac{-3+10}{15}x^{5} & -1.7 & \\
& & & & \\
= & -\frac{5}{12}x^{9} & +\frac{7}{15}x^{5} & -1.7 &
\end{array} $
