Answer:
[tex]10x^{2} + 3x - 6[/tex]
Step-by-step explanation:
[tex]3x^{2} - 5x + 9 + 7x^{2} + 8x - 15[/tex]
combine like terms
[tex](3x^{2} + 7x^{2} ) + (-5x + 8x) + (9 - 15)[/tex]
