Answer
$-3y^{2}-15y+28$
Work Step by Step
Subtract the polynomials inside the first brackets
$ \begin{array}{llll}
& 7y^{2} & -4y & +2 \\
-( & 12y^{2} & +3y & -5)\\
\hline & & & \\
= & -5y^{2} & -7y & +7\\
& & &
\end{array} $
Add the polynomials in the second brackets:
$ \begin{array}{llll}
& 5y^{2} & -2y & -8 \\
+( & -7y^{2} & +10y & -13)\\
\hline & & & \\
= & -2y^{2} & +8y & -21
\end{array} $
Now subtract the results of the brackets:
$ \begin{array}{llll}
& -5y^{2} & -7y & +7\\
-( & -2y^{2} & +8y & -21)\\
\hline & & & \\
= & -3y^{2} & -15y & +28
\end{array} $
