Like terms are those terms which have the same power of the variable. Here, $4x^2$ and $8x^2$ are like terms, $6x$ and $9x$ are like terms, and $-7$ and $-2$ are like terms. So, we can rewrite the expression as follows:
$$(4x^2 + 8x^2) + (6x + 9x) + (-7 - 2)$$
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