6a + 12 = 2(3a - 8)
First, expand. / Your problem should look like: 6a + 12 = 6a - 16.
Second, cancel 6a on both sides. / Your problem should look like: 12 = -16.
Third, since 12 = -16 is false, there is no solution.
The equation is invalid, therefore there is no solution to it.