Distribute the -2 first on the right side of the equation
-3x-4=-2x+(-4)-x
-3x-4=-2x-4-x
Then add all like terms
-3x-4=-3x-4
Put all like terms on the same side ( variables on one side and constants on one side) when doing that remember when move a term from the original position it changes sign.
-3x+3x=4-4
0=0
There is no solution for x.