Simplify the Expression: a + 3(4a-6) Using Distribution

To solve the problem of simplifying the expression $a+3(4a-6)$, follow these detailed steps:

• Step 1: Distribute 3 across the terms in the parentheses.
  This means multiplying 3 with each term inside: $4a$ and $-6$.
• Step 2: Perform the multiplication:
  $3 \times 4a = 12a$
  $3 \times (-6) = -18$
• Step 3: Combine the distributed terms with $a$:
  Start with the given expression, $a + 12a - 18$.
• Step 4: Simplify by combining like terms:
  Add the coefficients of $a$: $a + 12a = 13a$.
• Step 5: Form the final expression:
  The simplified expression is $13a - 18$.

Therefore, the solution to the problem is $13a - 18$, which corresponds to choice 2.