Answer :
[tex]\begin{gathered} \text{first we will rrderthe terms, first, the ones with an "a" , then the ones with a "b"} \\ 10a-7b+11+8a-b-12=10a+8a-7b-b+11-12 \\ =(10a+8a)+(-7b-b)+(11-12) \\ =18a-8b-1 \\ \end{gathered}[/tex]
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[tex]\begin{gathered} \text{first we will rrderthe terms, first, the ones with an "a" , then the ones with a "b"} \\ 10a-7b+11+8a-b-12=10a+8a-7b-b+11-12 \\ =(10a+8a)+(-7b-b)+(11-12) \\ =18a-8b-1 \\ \end{gathered}[/tex]