There is no solution since the equation is inconsistent.
The equation does not have a solution.
x = 0 and y = 4
Without an indication of the equals sign, this is not an equation.
Not sure what you mean; that equation certainly has a solution.
x = 19
It is a linear equation in x. The equation has the solution x = 0.
One equation with two unknowns usually does not have a solution.
That is not a correct equation. The numbers on the left equal -16, not 0. This is an equation with no solution.
The solution is (x, y, z) = (2.5, 1, 2.5).