Simplify 9 + 3 ( 4a - 7 ) - 5a + 6

To simplify the expression, we can start by distributing the 3 to each term inside the parentheses:

9 + 3(4a - 7) - 5a + 6

= 9 + 12a - 21 - 5a + 6

Next, we can combine like terms:

= (12a - 5a) + (9 - 21 + 6)

= 7a + (-6)

= 7a - 6

So, the simplified expression is 7a - 6.