11. Perimeter = All Sides added together.
Remember there are two of each side with the expression.
Expression: 3b + 3b + b+a + b+ a
To simplify collect all like terms (ones with a common letter or are the same)
Simplified expression: 8b + 2a
You got the expression by adding all sides together then simplifying by collecting like terms.
I will do the rest as comments on this post.
