It means that a certain condition is not satisfied, or fulfilled, no matter what value you assign to the variable "x".
If you mean: 5x = 10 then the value of x is 2
If the value (not mean value) of y is related negatively to the value of x then larger values of x are associated with smaller values of y.
Do you mean "what is the value of x when 3x - 2x = 15?" in that case, the value of x is 15
that means the value of x is same as the value of y
X means the answer
If you mean: x+y = 30 and the value of y is 15 then the value of x is also 15
Residual point
If you mean: x-3 = 2x-8 then the value of x works out as 5
If you mean 2x = 28 then the value of x is 14
If you mean: 7x-30 = 180 then the value of x is 30
That depends on the value of x, and the value of c. The expression "x + c" can't be simplified, if that's what you mean.
If you mean -11x-5(x-12) = 252 then the value of x works out as -12