Explanation: For the following expression
[tex]12a+(-3b)-5a+9b[/tex]We can see there are different terms. There are terms with an "a" and others with a "b", so the first step is to rearrange our expression to make equal terms near each other as follows
[tex]\begin{gathered} 12a+(-3b)-5a+9b \\ 12a-5a+(-3b)+9b \end{gathered}[/tex]Now we can see above there is "12a - 5a" on the left and "+(-3b) + 9b" on the right we do that because they are like terms.
Also, we know that "+(-3b) means -3b once when we have a positive sign outside and a negative sign inside it is equal to just one negative sign" so we can simplify to
[tex]\begin{gathered} 12a-5a+(-3b)+9b \\ 12a-5a-3b+9b \end{gathered}[/tex]Now we can operate like terms as follows
Final answer: So the final answer is
[tex]7a+6b_{}[/tex].
