To finish the equation so that it has an infinite number of solutions, we can set the left side equal to the right side of the equation and ensure they are equivalent.
Starting with your equation:
\[ (6x + 3) - 4 = ? \]
First, simplify the left side:
\[ 6x + 3 - 4 = 6x - 1 \]
Now, we can set the equation equal to itself:
\[ 6x - 1 = 6x - 1 \]
This statement will hold true for all values of \( x \), giving us an infinite number of solutions.
Thus, the finished equation is:
\[ (6x + 3) - 4 = 6x - 1 \]