Simplify the expression: 6(2x + 3) - 4x.

To simplify the expression 6(2x + 3) - 4x, start by distributing the 6 to both terms inside the parentheses:

6(2x) + 6(3) results in 12x + 18.

Next, combine this with the -4x from the original expression:

12x + 18 - 4x.

Now, combine the like terms (12x and -4x):

12x - 4x equals 8x.

So, the expression simplifies to 8x + 18, which matches the choice provided.

This process illustrates how careful distribution and combining like terms can lead to a simplified expression. The final result, 8x + 18, clearly shows the relationships between the components of the original expression.