Question

How do you make 3x-7=(blank)x+12 have no solution?

Answer 1

Answer: put 3 in the blank

Explanation:

$3x-7=3x+12\,\,\,|-3x\\-7 = 12$

The last row shows that this equation will never be true no matter what value of x. This shows that setting the coefficient of x to 3 makes the equation have no solutions.