Hi!
[tex]3a+3b=12[/tex]
[tex]3a+3b-3b=12-3b[/tex]
[tex]3a=12-3b[/tex]
[tex]\frac{3a}{3}=\frac{12}{3}-\frac{3b}{3}[/tex]
[tex]a=-b+4[/tex]
Explanation: First you had to subtract 3b from both sides. Then simplify and it gave us 3a=12-3b. Next you can also divide by 3 from both sides. It gave us 3a/3=12/3-3b/3. Then simplify again, it gave us the answer is a=-b+4 is the right answer. Hope this helps! And thank you for posting your question at here on Brainly. And have a great day! -Charlie
