The expression $a + 2b$ is greater than $b - a$ by:

$(a + 2b) - (b - a)$

First, distribute the negative sign:

$a + 2b - b + a$

Combine like terms:

$2a + b$

So, $a + 2b$ is $2a + b$ greater than $b - a$.

Would you like a more detailed explanation or have any questions?

Related Questions:

1. If $a = 3$ and $b = 2$, what is the value of $2a + b$?
2. How would the expression change if both $a$ and $b$ are negative?
3. What happens to the difference $2a + b$ if $a$ is doubled?
4. If $a = b$, what is the resulting difference between $a + 2b$ and $b - a$?
5. How would the difference change if you add a constant $c$ to both $a + 2b$ and $b - a$?

Tip:

Always remember to carefully distribute negative signs when subtracting expressions.