Answer
Yes, the expressions are equivalent.
Work Step by Step
We start with the first expression: $(6+b)+a$
The associative property of addition states that changing the grouping of the addends does not affect the sum.
We use this property to change the grouping of the addends: $6+(b+a)$
The commutative property of addition states that changing the order of the addends does not affect the sum.
We use this property to change the order of the addends: $6+(a+b)$
Since this expression is the same as the second expression, the expressions are equivalent.