To simplify the expression 3(a+2)-5a+3, we follow these steps: First, we distribute the 3 to the terms inside the parentheses, which gives us 3a + 6. Next, we rewrite the expression as 3a + 6 - 5a + 3. Then, we combine like terms: we have (3a - 5a) which simplifies to -2a, and (6 + 3) which simplifies to 9. Therefore, the final simplified expression is -2a + 9.