Simplify 7a + 8b + 4a + 9b: Combining Like Terms Step by Step

To simplify the expression $7a + 8b + 4a + 9b$, we will follow these steps:

• Step 1: Identify like terms. The expression contains terms involving $a$ ($7a$ and $4a$) and terms involving $b$ ($8b$ and $9b$).
• Step 2: Combine the coefficients of like terms.
• Step 3: Rewrite the simplified expression.

Step 1: The like terms involving $a$ are $7a$ and $4a$.

Step 2: Add these coefficients: $7 + 4 = 11$. Therefore, the combined term for $a$ is $11a$.

Step 3: The like terms involving $b$ are $8b$ and $9b$.

Step 4: Add these coefficients: $8 + 9 = 17$. Therefore, the combined term for $b$ is $17b$.

Thus, the expression simplifies to $11a + 17b$.

The correct answer choice is: $11a + 17b$.