(a-b)+(b+a)=

To simplify the expression \((a - b) + (b + a)\), we can first rewrite the expression by removing the parentheses:

\[ a - b + b + a \]

Now, we can combine like terms. The \(a\) terms add together, and the \(b\) terms cancel each other out:

\[ a + a - b + b = 2a \]

Therefore, the simplified expression is:

\[ 2a \]