To create an equation with no solution, we need to set up an equation where the two sides are parallel and hence never equal.
One way to do this is by ensuring that the coefficients of \( x \) on both sides are the same but the constant terms are different.
For the equation:
\[ 5x + 12 = \text{BLANK}x + 9 \]
We can choose the blank to be 5 (to match the coefficient of \( x \) on the left side) and then select a constant that does not equal 12 when added to 9. For example:
Choose the blank to be 5.
Then we have:
\[ 5x + 12 = 5x + 9 \]
This simplifies to:
\[ 12 = 9 \]
Which is a contradiction and thus has no solution.
So, the complete equation is:
\[ 5x + 12 = 5x + 9 \]