[tex]\boxed{\underline{\bf \: ANSWER}}[/tex]
[tex] \tt {4x}^{2} y + 2xy - 6 + 5 {x}^{2} y - 8xy + 13 \\ \\ \sf Place \: like \: terms \: together. \\ \\ \tt = {4x}^{2} y + {5x}^{2} y + 2xy - 8xy - 6 + 13 \\ \\ \sf Now \: combine \: the \: like \: terms. \\ \\ = \boxed{\bf \: 9 {x}^{2} y - 6xy + 7}[/tex]
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Hope it helps. Good luck :)
RainbowSalt2222