Answer
$9x^2+8$
Work Step by Step
The sum of $5x^2-3x+6$ and $4x^2+5x-3$ is
\begin{array}{l}\require{cancel}
5x^2-3x+6+4x^2+5x-3
\\\\=
(5x^2+4x^2)+(-3x+5x)+(6-3)
\\\\=
9x^2+2x+3
.\end{array}
Subtracting $2x-5$ from the previous result, then,
\begin{array}{l}\require{cancel}
9x^2+2x+3-(2x-5)
\\\\=
9x^2+2x+3-2x+5
\\\\=
9x^2+(2x-2x)+(3+5)
\\\\=
9x^2+8
.\end{array}
