Final answer:
To combine like terms, add or subtract the coefficients of the variables. In this case, the expression simplifies to x+19.
Step-by-step explanation:
To combine like terms, we add or subtract the coefficients of the variables that have the same term. In this case, the like terms are 7x, -12x, and 6x. Adding the coefficients, we get 1x. So, the expression can be simplified to x+19.
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