The given expression is
[tex]-x^2-3xy+6y+2x^2-8+5xy-x^2+14[/tex]We have to combine like terms, let's organize the terms first
[tex]-x^2+2x^2-x^2-3xy+5xy+6y-8+14[/tex]Now, we reduce them
[tex]\begin{gathered} -2x^2+2x^2-3xy+5xy+6y-8+14 \\ 0x^2+2xy+6y+6 \\ 2xy+6y+6 \end{gathered}[/tex]