Not sure what you mean; that equation certainly has a solution.
It is a linear equation in x. The equation has the solution x = 0.
x = 0 and y = 4
An equation, solution x = -10
It does if x=2. That's the solution of your equation.
2x + 4 = 8Subtract 4 from each side of the equation:2x = 4Divide each side by 2:x = 2
the answer is y minus 10 divided by 2.
2x + 4 is an expression, not an equation. There can be no solution set for an expression.
-2x plus 3y equals 1
It appears to be a simple linear equation in 'x'. But it has no solution. There is no numerical value for 'x' that can make it a true statement.
The solution is (x, y, z) = (2.5, 1, 2.5).